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1.2       lievre     22: 
1.6       lievre     23: <h1 align="center"><font color="#00006A">Computing Health
                     24: Expectancies using IMaCh</font></h1>
1.2       lievre     25: 
1.6       lievre     26: <h1 align="center"><font color="#00006A" size="5">(a Maximum
                     27: Likelihood Computer Program using Interpolation of Markov Chains)</font></h1>
                     28: 
                     29: <p align="center">&nbsp;</p>
                     30: 
                     31: <p align="center"><a href="http://www.ined.fr/"><img
                     32: src="logo-ined.gif" border="0" width="151" height="76"></a><img
                     33: src="euroreves2.gif" width="151" height="75"></p>
                     34: 
                     35: <h3 align="center"><a href="http://www.ined.fr/"><font
                     36: color="#00006A">INED</font></a><font color="#00006A"> and </font><a
                     37: href="http://euroreves.ined.fr"><font color="#00006A">EUROREVES</font></a></h3>
                     38: 
                     39: <p align="center"><font color="#00006A" size="4"><strong>Version
1.7       brouard    40: 0.71a, March 2002</strong></font></p>
1.6       lievre     41: 
                     42: <hr size="3" color="#EC5E5E">
                     43: 
                     44: <p align="center"><font color="#00006A"><strong>Authors of the
                     45: program: </strong></font><a href="http://sauvy.ined.fr/brouard"><font
                     46: color="#00006A"><strong>Nicolas Brouard</strong></font></a><font
                     47: color="#00006A"><strong>, senior researcher at the </strong></font><a
                     48: href="http://www.ined.fr"><font color="#00006A"><strong>Institut
                     49: National d'Etudes Démographiques</strong></font></a><font
                     50: color="#00006A"><strong> (INED, Paris) in the &quot;Mortality,
                     51: Health and Epidemiology&quot; Research Unit </strong></font></p>
                     52: 
                     53: <p align="center"><font color="#00006A"><strong>and Agnès
                     54: Lièvre<br clear="left">
                     55: </strong></font></p>
                     56: 
                     57: <h4><font color="#00006A">Contribution to the mathematics: C. R.
                     58: Heathcote </font><font color="#00006A" size="2">(Australian
                     59: National University, Canberra).</font></h4>
                     60: 
                     61: <h4><font color="#00006A">Contact: Agnès Lièvre (</font><a
                     62: href="mailto:lievre@ined.fr"><font color="#00006A"><i>lievre@ined.fr</i></font></a><font
                     63: color="#00006A">) </font></h4>
1.2       lievre     64: 
                     65: <hr>
1.6       lievre     66: 
                     67: <ul>
                     68:     <li><a href="#intro">Introduction</a> </li>
                     69:     <li><a href="#data">On what kind of data can it be used?</a></li>
                     70:     <li><a href="#datafile">The data file</a> </li>
                     71:     <li><a href="#biaspar">The parameter file</a> </li>
                     72:     <li><a href="#running">Running Imach</a> </li>
                     73:     <li><a href="#output">Output files and graphs</a> </li>
                     74:     <li><a href="#example">Exemple</a> </li>
1.2       lievre     75: </ul>
1.6       lievre     76: 
1.2       lievre     77: <hr>
                     78: 
1.6       lievre     79: <h2><a name="intro"><font color="#00006A">Introduction</font></a></h2>
1.2       lievre     80: 
1.6       lievre     81: <p>This program computes <b>Healthy Life Expectancies</b> from <b>cross-longitudinal
                     82: data</b> using the methodology pioneered by Laditka and Wolf (1).
                     83: Within the family of Health Expectancies (HE), Disability-free
                     84: life expectancy (DFLE) is probably the most important index to
1.2       lievre     85: monitor. In low mortality countries, there is a fear that when
                     86: mortality declines, the increase in DFLE is not proportionate to
                     87: the increase in total Life expectancy. This case is called the <em>Expansion
                     88: of morbidity</em>. Most of the data collected today, in
1.7       brouard    89: particular by the international <a href="http://www.reves.org">REVES</a>
1.2       lievre     90: network on Health expectancy, and most HE indices based on these
                     91: data, are <em>cross-sectional</em>. It means that the information
                     92: collected comes from a single cross-sectional survey: people from
                     93: various ages (but mostly old people) are surveyed on their health
                     94: status at a single date. Proportion of people disabled at each
                     95: age, can then be measured at that date. This age-specific
                     96: prevalence curve is then used to distinguish, within the
                     97: stationary population (which, by definition, is the life table
                     98: estimated from the vital statistics on mortality at the same
                     99: date), the disable population from the disability-free
                    100: population. Life expectancy (LE) (or total population divided by
                    101: the yearly number of births or deaths of this stationary
                    102: population) is then decomposed into DFLE and DLE. This method of
                    103: computing HE is usually called the Sullivan method (from the name
1.6       lievre    104: of the author who first described it).</p>
1.2       lievre    105: 
1.6       lievre    106: <p>Age-specific proportions of people disable are very difficult
                    107: to forecast because each proportion corresponds to historical
                    108: conditions of the cohort and it is the result of the historical
                    109: flows from entering disability and recovering in the past until
                    110: today. The age-specific intensities (or incidence rates) of
                    111: entering disability or recovering a good health, are reflecting
                    112: actual conditions and therefore can be used at each age to
                    113: forecast the future of this cohort. For example if a country is
                    114: improving its technology of prosthesis, the incidence of
                    115: recovering the ability to walk will be higher at each (old) age,
                    116: but the prevalence of disability will only slightly reflect an
                    117: improve because the prevalence is mostly affected by the history
                    118: of the cohort and not by recent period effects. To measure the
                    119: period improvement we have to simulate the future of a cohort of
                    120: new-borns entering or leaving at each age the disability state or
                    121: dying according to the incidence rates measured today on
                    122: different cohorts. The proportion of people disabled at each age
                    123: in this simulated cohort will be much lower (using the exemple of
                    124: an improvement) that the proportions observed at each age in a
                    125: cross-sectional survey. This new prevalence curve introduced in a
                    126: life table will give a much more actual and realistic HE level
                    127: than the Sullivan method which mostly measured the History of
                    128: health conditions in this country.</p>
                    129: 
                    130: <p>Therefore, the main question is how to measure incidence rates
                    131: from cross-longitudinal surveys? This is the goal of the IMaCH
                    132: program. From your data and using IMaCH you can estimate period
                    133: HE and not only Sullivan's HE. Also the standard errors of the HE
                    134: are computed.</p>
                    135: 
                    136: <p>A cross-longitudinal survey consists in a first survey
                    137: (&quot;cross&quot;) where individuals from different ages are
                    138: interviewed on their health status or degree of disability. At
                    139: least a second wave of interviews (&quot;longitudinal&quot;)
                    140: should measure each new individual health status. Health
                    141: expectancies are computed from the transitions observed between
                    142: waves and are computed for each degree of severity of disability
                    143: (number of life states). More degrees you consider, more time is
                    144: necessary to reach the Maximum Likelihood of the parameters
                    145: involved in the model. Considering only two states of disability
                    146: (disable and healthy) is generally enough but the computer
                    147: program works also with more health statuses.<br>
1.2       lievre    148: <br>
                    149: The simplest model is the multinomial logistic model where <i>pij</i>
                    150: is the probability to be observed in state <i>j</i> at the second
                    151: wave conditional to be observed in state <em>i</em> at the first
                    152: wave. Therefore a simple model is: log<em>(pij/pii)= aij +
                    153: bij*age+ cij*sex,</em> where '<i>age</i>' is age and '<i>sex</i>'
                    154: is a covariate. The advantage that this computer program claims,
                    155: comes from that if the delay between waves is not identical for
                    156: each individual, or if some individual missed an interview, the
                    157: information is not rounded or lost, but taken into account using
                    158: an interpolation or extrapolation. <i>hPijx</i> is the
                    159: probability to be observed in state <i>i</i> at age <i>x+h</i>
                    160: conditional to the observed state <i>i</i> at age <i>x</i>. The
                    161: delay '<i>h</i>' can be split into an exact number (<i>nh*stepm</i>)
                    162: of unobserved intermediate states. This elementary transition (by
                    163: month or quarter trimester, semester or year) is modeled as a
                    164: multinomial logistic. The <i>hPx</i> matrix is simply the matrix
                    165: product of <i>nh*stepm</i> elementary matrices and the
                    166: contribution of each individual to the likelihood is simply <i>hPijx</i>.
1.6       lievre    167: <br>
                    168: </p>
1.2       lievre    169: 
1.6       lievre    170: <p>The program presented in this manual is a quite general
                    171: program named <strong>IMaCh</strong> (for <strong>I</strong>nterpolated
                    172: <strong>MA</strong>rkov <strong>CH</strong>ain), designed to
                    173: analyse transition data from longitudinal surveys. The first step
                    174: is the parameters estimation of a transition probabilities model
                    175: between an initial status and a final status. From there, the
                    176: computer program produces some indicators such as observed and
                    177: stationary prevalence, life expectancies and their variances and
                    178: graphs. Our transition model consists in absorbing and
                    179: non-absorbing states with the possibility of return across the
                    180: non-absorbing states. The main advantage of this package,
1.2       lievre    181: compared to other programs for the analysis of transition data
1.6       lievre    182: (For example: Proc Catmod of SAS<sup>®</sup>) is that the whole
1.2       lievre    183: individual information is used even if an interview is missing, a
                    184: status or a date is unknown or when the delay between waves is
                    185: not identical for each individual. The program can be executed
                    186: according to parameters: selection of a sub-sample, number of
                    187: absorbing and non-absorbing states, number of waves taken in
                    188: account (the user inputs the first and the last interview), a
                    189: tolerance level for the maximization function, the periodicity of
1.5       lievre    190: the transitions (we can compute annual, quarterly or monthly
1.2       lievre    191: transitions), covariates in the model. It works on Windows or on
1.6       lievre    192: Unix.<br>
                    193: </p>
1.2       lievre    194: 
                    195: <hr>
                    196: 
1.6       lievre    197: <p>(1) Laditka, Sarah B. and Wolf, Douglas A. (1998), &quot;New
1.2       lievre    198: Methods for Analyzing Active Life Expectancy&quot;. <i>Journal of
1.6       lievre    199: Aging and Health</i>. Vol 10, No. 2. </p>
1.2       lievre    200: 
                    201: <hr>
                    202: 
1.6       lievre    203: <h2><a name="data"><font color="#00006A">On what kind of data can
                    204: it be used?</font></a></h2>
1.2       lievre    205: 
1.6       lievre    206: <p>The minimum data required for a transition model is the
                    207: recording of a set of individuals interviewed at a first date and
                    208: interviewed again at least one another time. From the
                    209: observations of an individual, we obtain a follow-up over time of
                    210: the occurrence of a specific event. In this documentation, the
                    211: event is related to health status at older ages, but the program
                    212: can be applied on a lot of longitudinal studies in different
                    213: contexts. To build the data file explained into the next section,
                    214: you must have the month and year of each interview and the
                    215: corresponding health status. But in order to get age, date of
                    216: birth (month and year) is required (missing values is allowed for
                    217: month). Date of death (month and year) is an important
                    218: information also required if the individual is dead. Shorter
                    219: steps (i.e. a month) will more closely take into account the
                    220: survival time after the last interview.</p>
1.2       lievre    221: 
                    222: <hr>
                    223: 
1.6       lievre    224: <h2><a name="datafile"><font color="#00006A">The data file</font></a></h2>
1.2       lievre    225: 
1.6       lievre    226: <p>In this example, 8,000 people have been interviewed in a
                    227: cross-longitudinal survey of 4 waves (1984, 1986, 1988, 1990).
                    228: Some people missed 1, 2 or 3 interviews. Health statuses are
                    229: healthy (1) and disable (2). The survey is not a real one. It is
                    230: a simulation of the American Longitudinal Survey on Aging. The
                    231: disability state is defined if the individual missed one of four
                    232: ADL (Activity of daily living, like bathing, eating, walking).
                    233: Therefore, even is the individuals interviewed in the sample are
                    234: virtual, the information brought with this sample is close to the
                    235: situation of the United States. Sex is not recorded is this
                    236: sample.</p>
                    237: 
                    238: <p>Each line of the data set (named <a href="data1.txt">data1.txt</a>
                    239: in this first example) is an individual record which fields are: </p>
                    240: 
                    241: <ul>
                    242:     <li><b>Index number</b>: positive number (field 1) </li>
                    243:     <li><b>First covariate</b> positive number (field 2) </li>
                    244:     <li><b>Second covariate</b> positive number (field 3) </li>
                    245:     <li><a name="Weight"><b>Weight</b></a>: positive number
                    246:         (field 4) . In most surveys individuals are weighted
                    247:         according to the stratification of the sample.</li>
                    248:     <li><b>Date of birth</b>: coded as mm/yyyy. Missing dates are
                    249:         coded as 99/9999 (field 5) </li>
                    250:     <li><b>Date of death</b>: coded as mm/yyyy. Missing dates are
                    251:         coded as 99/9999 (field 6) </li>
                    252:     <li><b>Date of first interview</b>: coded as mm/yyyy. Missing
                    253:         dates are coded as 99/9999 (field 7) </li>
                    254:     <li><b>Status at first interview</b>: positive number.
                    255:         Missing values ar coded -1. (field 8) </li>
                    256:     <li><b>Date of second interview</b>: coded as mm/yyyy.
                    257:         Missing dates are coded as 99/9999 (field 9) </li>
                    258:     <li><strong>Status at second interview</strong> positive
                    259:         number. Missing values ar coded -1. (field 10) </li>
                    260:     <li><b>Date of third interview</b>: coded as mm/yyyy. Missing
                    261:         dates are coded as 99/9999 (field 11) </li>
                    262:     <li><strong>Status at third interview</strong> positive
                    263:         number. Missing values ar coded -1. (field 12) </li>
                    264:     <li><b>Date of fourth interview</b>: coded as mm/yyyy.
                    265:         Missing dates are coded as 99/9999 (field 13) </li>
                    266:     <li><strong>Status at fourth interview</strong> positive
                    267:         number. Missing values are coded -1. (field 14) </li>
                    268:     <li>etc</li>
1.2       lievre    269: </ul>
                    270: 
1.6       lievre    271: <p>&nbsp;</p>
1.2       lievre    272: 
1.6       lievre    273: <p>If your longitudinal survey do not include information about
                    274: weights or covariates, you must fill the column with a number
                    275: (e.g. 1) because a missing field is not allowed.</p>
1.2       lievre    276: 
                    277: <hr>
                    278: 
1.6       lievre    279: <h2><font color="#00006A">Your first example parameter file</font><a
                    280: href="http://euroreves.ined.fr/imach"></a><a name="uio"></a></h2>
1.2       lievre    281: 
1.7       brouard   282: <h2><a name="biaspar"></a>#Imach version 0.71a, March 2002,
1.6       lievre    283: INED-EUROREVES </h2>
1.2       lievre    284: 
1.6       lievre    285: <p>This is a comment. Comments start with a '#'.</p>
1.2       lievre    286: 
1.6       lievre    287: <h4><font color="#FF0000">First uncommented line</font></h4>
                    288: 
                    289: <pre>title=1st_example datafile=data1.txt lastobs=8600 firstpass=1 lastpass=4</pre>
                    290: 
                    291: <ul>
                    292:     <li><b>title=</b> 1st_example is title of the run. </li>
                    293:     <li><b>datafile=</b>data1.txt is the name of the data set.
                    294:         Our example is a six years follow-up survey. It consists
                    295:         in a baseline followed by 3 reinterviews. </li>
                    296:     <li><b>lastobs=</b> 8600 the program is able to run on a
                    297:         subsample where the last observation number is lastobs.
                    298:         It can be set a bigger number than the real number of
                    299:         observations (e.g. 100000). In this example, maximisation
                    300:         will be done on the 8600 first records. </li>
                    301:     <li><b>firstpass=1</b> , <b>lastpass=4 </b>In case of more
                    302:         than two interviews in the survey, the program can be run
                    303:         on selected transitions periods. firstpass=1 means the
                    304:         first interview included in the calculation is the
                    305:         baseline survey. lastpass=4 means that the information
                    306:         brought by the 4th interview is taken into account.</li>
1.2       lievre    307: </ul>
                    308: 
1.6       lievre    309: <p>&nbsp;</p>
                    310: 
                    311: <h4><a name="biaspar-2"><font color="#FF0000">Second uncommented
                    312: line</font></a></h4>
1.2       lievre    313: 
1.6       lievre    314: <pre>ftol=1.e-08 stepm=1 ncov=2 nlstate=2 ndeath=1 maxwav=4 mle=1 weight=0</pre>
                    315: 
                    316: <ul>
                    317:     <li><b>ftol=1e-8</b> Convergence tolerance on the function
                    318:         value in the maximisation of the likelihood. Choosing a
                    319:         correct value for ftol is difficult. 1e-8 is a correct
                    320:         value for a 32 bits computer.</li>
                    321:     <li><b>stepm=1</b> Time unit in months for interpolation.
                    322:         Examples:<ul>
                    323:             <li>If stepm=1, the unit is a month </li>
                    324:             <li>If stepm=4, the unit is a trimester</li>
                    325:             <li>If stepm=12, the unit is a year </li>
                    326:             <li>If stepm=24, the unit is two years</li>
                    327:             <li>... </li>
1.2       lievre    328:         </ul>
                    329:     </li>
1.8     ! lievre    330:     <li><b>ncov=2</b> Number of covariates in the datafile. </li>
1.6       lievre    331:     <li><b>nlstate=2</b> Number of non-absorbing (alive) states.
                    332:         Here we have two alive states: disability-free is coded 1
                    333:         and disability is coded 2. </li>
                    334:     <li><b>ndeath=1</b> Number of absorbing states. The absorbing
                    335:         state death is coded 3. </li>
                    336:     <li><b>maxwav=4</b> Number of waves in the datafile.</li>
                    337:     <li><a name="mle"><b>mle</b></a><b>=1</b> Option for the
                    338:         Maximisation Likelihood Estimation. <ul>
                    339:             <li>If mle=1 the program does the maximisation and
                    340:                 the calculation of health expectancies </li>
                    341:             <li>If mle=0 the program only does the calculation of
                    342:                 the health expectancies. </li>
1.2       lievre    343:         </ul>
                    344:     </li>
1.6       lievre    345:     <li><b>weight=0</b> Possibility to add weights. <ul>
                    346:             <li>If weight=0 no weights are included </li>
                    347:             <li>If weight=1 the maximisation integrates the
                    348:                 weights which are in field <a href="#Weight">4</a></li>
1.2       lievre    349:         </ul>
                    350:     </li>
                    351: </ul>
                    352: 
1.6       lievre    353: <h4><font color="#FF0000">Covariates</font></h4>
                    354: 
                    355: <p>Intercept and age are systematically included in the model.
1.8     ! lievre    356: Additional covariates can be included with the command: </p>
1.2       lievre    357: 
1.6       lievre    358: <pre>model=<em>list of covariates</em></pre>
                    359: 
                    360: <ul>
                    361:     <li>if<strong> model=. </strong>then no covariates are
                    362:         included</li>
                    363:     <li>if <strong>model=V1</strong> the model includes the first
                    364:         covariate (field 2)</li>
                    365:     <li>if <strong>model=V2 </strong>the model includes the
                    366:         second covariate (field 3)</li>
                    367:     <li>if <strong>model=V1+V2 </strong>the model includes the
                    368:         first and the second covariate (fields 2 and 3)</li>
                    369:     <li>if <strong>model=V1*V2 </strong>the model includes the
1.2       lievre    370:         product of the first and the second covariate (fields 2
1.6       lievre    371:         and 3)</li>
                    372:     <li>if <strong>model=V1+V1*age</strong> the model includes
                    373:         the product covariate*age</li>
1.2       lievre    374: </ul>
                    375: 
1.8     ! lievre    376: <p>In this example, we have two covariates in the data file
        !           377: (fields 2 and 3). The number of covariates is defined with
        !           378: statement ncov=2. If now you have 3 covariates in the datafile
        !           379: (fields 2, 3 and 4), you have to set ncov=3. Then you can run the
        !           380: programme with a new parametrisation taking into account the
        !           381: third covariate. For example, <strong>model=V1+V3 </strong>estimates
        !           382: a model with the first and third covariates. More complicated
        !           383: models can be used, but it will takes more time to converge. With
        !           384: a simple model (no covariates), the programme estimates 8
        !           385: parameters. Adding covariates increases the number of parameters
        !           386: : 12 for <strong>model=V1, </strong>16 for <strong>model=V1+V1*age
        !           387: </strong>and 20 for <strong>model=V1+V2+V3.</strong></p>
        !           388: 
1.6       lievre    389: <h4><font color="#FF0000">Guess values for optimization</font><font
                    390: color="#00006A"> </font></h4>
                    391: 
                    392: <p>You must write the initial guess values of the parameters for
                    393: optimization. The number of parameters, <em>N</em> depends on the
1.2       lievre    394: number of absorbing states and non-absorbing states and on the
                    395: number of covariates. <br>
                    396: <em>N</em> is given by the formula <em>N</em>=(<em>nlstate</em> +
                    397: <em>ndeath</em>-1)*<em>nlstate</em>*<em>ncov</em>&nbsp;. <br>
                    398: <br>
                    399: Thus in the simple case with 2 covariates (the model is log
                    400: (pij/pii) = aij + bij * age where intercept and age are the two
                    401: covariates), and 2 health degrees (1 for disability-free and 2
                    402: for disability) and 1 absorbing state (3), you must enter 8
                    403: initials values, a12, b12, a13, b13, a21, b21, a23, b23. You can
                    404: start with zeros as in this example, but if you have a more
                    405: precise set (for example from an earlier run) you can enter it
                    406: and it will speed up them<br>
1.4       lievre    407: Each of the four lines starts with indices &quot;ij&quot;: <b>ij
1.6       lievre    408: aij bij</b> </p>
                    409: 
                    410: <blockquote>
                    411:     <pre># Guess values of aij and bij in log (pij/pii) = aij + bij * age
                    412: 12 -14.155633  0.110794 
                    413: 13  -7.925360  0.032091 
                    414: 21  -1.890135 -0.029473 
                    415: 23  -6.234642  0.022315 </pre>
                    416: </blockquote>
                    417: 
1.8     ! lievre    418: <p>or, to simplify (in most of cases it converges but there is no
        !           419: warranty!): </p>
1.6       lievre    420: 
                    421: <blockquote>
                    422:     <pre>12 0.0 0.0
                    423: 13 0.0 0.0
                    424: 21 0.0 0.0
                    425: 23 0.0 0.0</pre>
                    426: </blockquote>
                    427: 
                    428: <h4><font color="#FF0000">Guess values for computing variances</font></h4>
1.2       lievre    429: 
1.6       lievre    430: <p>This is an output if <a href="#mle">mle</a>=1. But it can be
                    431: used as an input to get the various output data files (Health
1.2       lievre    432: expectancies, stationary prevalence etc.) and figures without
1.6       lievre    433: rerunning the rather long maximisation phase (mle=0). </p>
1.2       lievre    434: 
1.6       lievre    435: <p>The scales are small values for the evaluation of numerical
1.2       lievre    436: derivatives. These derivatives are used to compute the hessian
                    437: matrix of the parameters, that is the inverse of the covariance
                    438: matrix, and the variances of health expectancies. Each line
                    439: consists in indices &quot;ij&quot; followed by the initial scales
1.6       lievre    440: (zero to simplify) associated with aij and bij. </p>
1.2       lievre    441: 
1.6       lievre    442: <ul>
                    443:     <li>If mle=1 you can enter zeros:</li>
1.2       lievre    444: </ul>
                    445: 
1.6       lievre    446: <blockquote>
                    447:     <pre># Scales (for hessian or gradient estimation)
                    448: 12 0. 0. 
                    449: 13 0. 0. 
                    450: 21 0. 0. 
                    451: 23 0. 0. </pre>
                    452: </blockquote>
                    453: 
                    454: <ul>
                    455:     <li>If mle=0 you must enter a covariance matrix (usually
                    456:         obtained from an earlier run).</li>
1.2       lievre    457: </ul>
                    458: 
1.6       lievre    459: <h4><font color="#FF0000">Covariance matrix of parameters</font></h4>
                    460: 
                    461: <p>This is an output if <a href="#mle">mle</a>=1. But it can be
                    462: used as an input to get the various output data files (Health
1.5       lievre    463: expectancies, stationary prevalence etc.) and figures without
1.6       lievre    464: rerunning the rather long maximisation phase (mle=0). </p>
1.2       lievre    465: 
1.6       lievre    466: <p>Each line starts with indices &quot;ijk&quot; followed by the
                    467: covariances between aij and bij: </p>
1.5       lievre    468: 
1.6       lievre    469: <pre>
                    470:    121 Var(a12) 
                    471:    122 Cov(b12,a12)  Var(b12) 
                    472:           ...
                    473:    232 Cov(b23,a12)  Cov(b23,b12) ... Var (b23) </pre>
1.2       lievre    474: 
1.6       lievre    475: <ul>
                    476:     <li>If mle=1 you can enter zeros. </li>
1.2       lievre    477: </ul>
                    478: 
1.6       lievre    479: <blockquote>
                    480:     <pre># Covariance matrix
                    481: 121 0.
                    482: 122 0. 0.
                    483: 131 0. 0. 0. 
                    484: 132 0. 0. 0. 0. 
                    485: 211 0. 0. 0. 0. 0. 
                    486: 212 0. 0. 0. 0. 0. 0. 
                    487: 231 0. 0. 0. 0. 0. 0. 0. 
                    488: 232 0. 0. 0. 0. 0. 0. 0. 0.</pre>
                    489: </blockquote>
                    490: 
                    491: <ul>
                    492:     <li>If mle=0 you must enter a covariance matrix (usually
                    493:         obtained from an earlier run).<br>
                    494:         </li>
1.2       lievre    495: </ul>
                    496: 
1.6       lievre    497: <h4><font color="#FF0000">Age range for calculation of stationary
                    498: prevalences and health expectancies</font></h4>
1.2       lievre    499: 
1.6       lievre    500: <pre>agemin=70 agemax=100 bage=50 fage=100</pre>
1.2       lievre    501: 
1.6       lievre    502: <p>Once we obtained the estimated parameters, the program is able
                    503: to calculated stationary prevalence, transitions probabilities
                    504: and life expectancies at any age. Choice of age range is useful
                    505: for extrapolation. In our data file, ages varies from age 70 to
1.8     ! lievre    506: 102. It is possible to get extrapolated stationary prevalence by
        !           507: age ranging from agemin to agemax. </p>
1.6       lievre    508: 
1.8     ! lievre    509: <p>Setting bage=50 (begin age) and fage=100 (final age), makes
        !           510: the program computing life expectancy from age 'bage' to age
        !           511: 'fage'. As we use a model, we can interessingly compute life
        !           512: expectancy on a wider age range than the age range from the data.
        !           513: But the model can be rather wrong on much larger intervals.
        !           514: Program is limited to around 120 for upper age!</p>
1.6       lievre    515: 
                    516: <ul>
                    517:     <li><b>agemin=</b> Minimum age for calculation of the
                    518:         stationary prevalence </li>
                    519:     <li><b>agemax=</b> Maximum age for calculation of the
                    520:         stationary prevalence </li>
                    521:     <li><b>bage=</b> Minimum age for calculation of the health
                    522:         expectancies </li>
                    523:     <li><b>fage=</b> Maximum age for calculation of the health
                    524:         expectancies </li>
1.2       lievre    525: </ul>
                    526: 
1.6       lievre    527: <h4><a name="Computing"><font color="#FF0000">Computing</font></a><font
                    528: color="#FF0000"> the observed prevalence</font></h4>
1.4       lievre    529: 
1.6       lievre    530: <pre>begin-prev-date=1/1/1984 end-prev-date=1/6/1988 </pre>
1.4       lievre    531: 
1.6       lievre    532: <p>Statements 'begin-prev-date' and 'end-prev-date' allow to
                    533: select the period in which we calculate the observed prevalences
                    534: in each state. In this example, the prevalences are calculated on
                    535: data survey collected between 1 january 1984 and 1 june 1988. </p>
                    536: 
                    537: <ul>
                    538:     <li><strong>begin-prev-date= </strong>Starting date
                    539:         (day/month/year)</li>
                    540:     <li><strong>end-prev-date= </strong>Final date
                    541:         (day/month/year)</li>
1.4       lievre    542: </ul>
                    543: 
1.6       lievre    544: <h4><font color="#FF0000">Population- or status-based health
                    545: expectancies</font></h4>
1.5       lievre    546: 
1.6       lievre    547: <pre>pop_based=0</pre>
1.5       lievre    548: 
1.8     ! lievre    549: <p>The program computes status-based health expectancies, i.e
        !           550: health expectancies which depends on your initial health state.
        !           551: If you are healthy your healthy life expectancy (e11) is higher
        !           552: than if you were disabled (e21, with e11 &gt; e21).<br>
        !           553: To compute a healthy life expectancy independant of the initial
        !           554: status we have to weight e11 and e21 according to the probability
        !           555: to be in each state at initial age or, with other word, according
        !           556: to the proportion of people in each state.<br>
        !           557: We prefer computing a 'pure' period healthy life expectancy based
        !           558: only on the transtion forces. Then the weights are simply the
        !           559: stationnary prevalences or 'implied' prevalences at the initial
        !           560: age.<br>
        !           561: Some other people would like to use the cross-sectional
        !           562: prevalences (the &quot;Sullivan prevalences&quot;) observed at
        !           563: the initial age during a period of time <a href="#Computing">defined
        !           564: just above</a>. </p>
1.7       brouard   565: 
                    566: <ul>
1.8     ! lievre    567:     <li><strong>popbased= 0 </strong>Health expectancies are
        !           568:         computed at each age from stationary prevalences
        !           569:         'expected' at this initial age.</li>
        !           570:     <li><strong>popbased= 1 </strong>Health expectancies are
        !           571:         computed at each age from cross-sectional 'observed'
        !           572:         prevalence at this initial age. As all the population is
        !           573:         not observed at the same exact date we define a short
        !           574:         period were the observed prevalence is computed.</li>
1.7       brouard   575: </ul>
                    576: 
                    577: <h4><font color="#FF0000">Prevalence forecasting ( Experimental)</font></h4>
1.5       lievre    578: 
1.6       lievre    579: <pre>starting-proj-date=1/1/1989 final-proj-date=1/1/1992 mov_average=0 </pre>
1.5       lievre    580: 
1.8     ! lievre    581: <p>Prevalence and population projections are only available if
        !           582: the interpolation unit is a month, i.e. stepm=1 and if there are
        !           583: no covariate. The programme estimates the prevalence in each
        !           584: state at a precise date expressed in day/month/year. The
        !           585: programme computes one forecasted prevalence a year from a
        !           586: starting date (1 january of 1989 in this example) to a final date
        !           587: (1 january 1992). The statement mov_average allows to compute
        !           588: smoothed forecasted prevalences with a five-age moving average
        !           589: centered at the mid-age of the five-age period. </p>
1.5       lievre    590: 
1.6       lievre    591: <ul>
                    592:     <li><strong>starting-proj-date</strong>= starting date
                    593:         (day/month/year) of forecasting</li>
                    594:     <li><strong>final-proj-date= </strong>final date
                    595:         (day/month/year) of forecasting</li>
                    596:     <li><strong>mov_average</strong>= smoothing with a five-age
                    597:         moving average centered at the mid-age of the five-age
                    598:         period. The command<strong> mov_average</strong> takes
                    599:         value 1 if the prevalences are smoothed and 0 otherwise.</li>
                    600: </ul>
1.5       lievre    601: 
1.6       lievre    602: <h4><font color="#FF0000">Last uncommented line : Population
                    603: forecasting </font></h4>
1.5       lievre    604: 
1.6       lievre    605: <pre>popforecast=0 popfile=pyram.txt popfiledate=1/1/1989 last-popfiledate=1/1/1992</pre>
1.5       lievre    606: 
1.6       lievre    607: <p>This command is available if the interpolation unit is a
1.7       brouard   608: month, i.e. stepm=1 and if popforecast=1. From a data file
                    609: including age and number of persons alive at the precise date
                    610: &#145;popfiledate&#146;, you can forecast the number of persons
                    611: in each state until date &#145;last-popfiledate&#146;. In this
                    612: example, the popfile <a href="pyram.txt"><b>pyram.txt</b></a>
                    613: includes real data which are the Japanese population in 1989.</p>
                    614: 
                    615: <ul type="disc">
                    616:     <li class="MsoNormal"
                    617:     style="TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l10 level1 lfo36; tab-stops: list 36.0pt"><b>popforecast=
                    618:         0 </b>Option for population forecasting. If
                    619:         popforecast=1, the programme does the forecasting<b>.</b></li>
                    620:     <li class="MsoNormal"
                    621:     style="TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l10 level1 lfo36; tab-stops: list 36.0pt"><b>popfile=
                    622:         </b>name of the population file</li>
                    623:     <li class="MsoNormal"
                    624:     style="TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l10 level1 lfo36; tab-stops: list 36.0pt"><b>popfiledate=</b>
                    625:         date of the population population</li>
                    626:     <li class="MsoNormal"
                    627:     style="TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l10 level1 lfo36; tab-stops: list 36.0pt"><b>last-popfiledate</b>=
                    628:         date of the last population projection&nbsp;</li>
                    629: </ul>
1.5       lievre    630: 
1.6       lievre    631: <hr>
1.5       lievre    632: 
1.6       lievre    633: <h2><a name="running"></a><font color="#00006A">Running Imach
                    634: with this example</font></h2>
1.5       lievre    635: 
1.6       lievre    636: <p>We assume that you entered your <a href="biaspar.imach">1st_example
                    637: parameter file</a> as explained <a href="#biaspar">above</a>. To
                    638: run the program you should click on the imach.exe icon and enter
                    639: the name of the parameter file which is for example <a
                    640: href="C:\usr\imach\mle\biaspar.txt">C:\usr\imach\mle\biaspar.txt</a>
                    641: (you also can click on the biaspar.txt icon located in <br>
                    642: <a href="C:\usr\imach\mle">C:\usr\imach\mle</a> and put it with
                    643: the mouse on the imach window).<br>
                    644: </p>
                    645: 
                    646: <p>The time to converge depends on the step unit that you used (1
                    647: month is cpu consuming), on the number of cases, and on the
                    648: number of variables.</p>
1.5       lievre    649: 
1.6       lievre    650: <p>The program outputs many files. Most of them are files which
                    651: will be plotted for better understanding.</p>
1.5       lievre    652: 
1.6       lievre    653: <hr>
1.5       lievre    654: 
1.6       lievre    655: <h2><a name="output"><font color="#00006A">Output of the program
                    656: and graphs</font> </a></h2>
1.5       lievre    657: 
1.6       lievre    658: <p>Once the optimization is finished, some graphics can be made
                    659: with a grapher. We use Gnuplot which is an interactive plotting
                    660: program copyrighted but freely distributed. A gnuplot reference
                    661: manual is available <a href="http://www.gnuplot.info/">here</a>. <br>
                    662: When the running is finished, the user should enter a caracter
                    663: for plotting and output editing. </p>
                    664: 
                    665: <p>These caracters are:</p>
                    666: 
                    667: <ul>
                    668:     <li>'c' to start again the program from the beginning.</li>
                    669:     <li>'e' opens the <a href="biaspar.htm"><strong>biaspar.htm</strong></a>
                    670:         file to edit the output files and graphs. </li>
                    671:     <li>'q' for exiting.</li>
                    672: </ul>
1.4       lievre    673: 
1.6       lievre    674: <h5><font size="4"><strong>Results files </strong></font><br>
                    675: <br>
                    676: <font color="#EC5E5E" size="3"><strong>- </strong></font><a
                    677: name="Observed prevalence in each state"><font color="#EC5E5E"
                    678: size="3"><strong>Observed prevalence in each state</strong></font></a><font
                    679: color="#EC5E5E" size="3"><strong> (and at first pass)</strong></font><b>:
                    680: </b><a href="prbiaspar.txt"><b>prbiaspar.txt</b></a><br>
                    681: </h5>
                    682: 
                    683: <p>The first line is the title and displays each field of the
                    684: file. The first column is age. The fields 2 and 6 are the
                    685: proportion of individuals in states 1 and 2 respectively as
                    686: observed during the first exam. Others fields are the numbers of
                    687: people in states 1, 2 or more. The number of columns increases if
                    688: the number of states is higher than 2.<br>
                    689: The header of the file is </p>
                    690: 
                    691: <pre># Age Prev(1) N(1) N Age Prev(2) N(2) N
                    692: 70 1.00000 631 631 70 0.00000 0 631
                    693: 71 0.99681 625 627 71 0.00319 2 627 
                    694: 72 0.97125 1115 1148 72 0.02875 33 1148 </pre>
                    695: 
                    696: <p>It means that at age 70, the prevalence in state 1 is 1.000
                    697: and in state 2 is 0.00 . At age 71 the number of individuals in
                    698: state 1 is 625 and in state 2 is 2, hence the total number of
                    699: people aged 71 is 625+2=627. <br>
                    700: </p>
                    701: 
                    702: <h5><font color="#EC5E5E" size="3"><b>- Estimated parameters and
                    703: covariance matrix</b></font><b>: </b><a href="rbiaspar.txt"><b>rbiaspar.txt</b></a></h5>
                    704: 
                    705: <p>This file contains all the maximisation results: </p>
                    706: 
                    707: <pre> -2 log likelihood= 21660.918613445392
                    708:  Estimated parameters: a12 = -12.290174 b12 = 0.092161 
                    709:                        a13 = -9.155590  b13 = 0.046627 
                    710:                        a21 = -2.629849  b21 = -0.022030 
                    711:                        a23 = -7.958519  b23 = 0.042614  
                    712:  Covariance matrix: Var(a12) = 1.47453e-001
                    713:                     Var(b12) = 2.18676e-005
                    714:                     Var(a13) = 2.09715e-001
                    715:                     Var(b13) = 3.28937e-005  
                    716:                     Var(a21) = 9.19832e-001
                    717:                     Var(b21) = 1.29229e-004
                    718:                     Var(a23) = 4.48405e-001
                    719:                     Var(b23) = 5.85631e-005 
                    720:  </pre>
                    721: 
                    722: <p>By substitution of these parameters in the regression model,
                    723: we obtain the elementary transition probabilities:</p>
                    724: 
                    725: <p><img src="pebiaspar1.gif" width="400" height="300"></p>
                    726: 
                    727: <h5><font color="#EC5E5E" size="3"><b>- Transition probabilities</b></font><b>:
                    728: </b><a href="pijrbiaspar.txt"><b>pijrbiaspar.txt</b></a></h5>
                    729: 
                    730: <p>Here are the transitions probabilities Pij(x, x+nh) where nh
                    731: is a multiple of 2 years. The first column is the starting age x
                    732: (from age 50 to 100), the second is age (x+nh) and the others are
                    733: the transition probabilities p11, p12, p13, p21, p22, p23. For
                    734: example, line 5 of the file is: </p>
                    735: 
                    736: <pre> 100 106 0.02655 0.17622 0.79722 0.01809 0.13678 0.84513 </pre>
                    737: 
                    738: <p>and this means: </p>
                    739: 
                    740: <pre>p11(100,106)=0.02655
                    741: p12(100,106)=0.17622
                    742: p13(100,106)=0.79722
                    743: p21(100,106)=0.01809
                    744: p22(100,106)=0.13678
                    745: p22(100,106)=0.84513 </pre>
                    746: 
                    747: <h5><font color="#EC5E5E" size="3"><b>- </b></font><a
                    748: name="Stationary prevalence in each state"><font color="#EC5E5E"
                    749: size="3"><b>Stationary prevalence in each state</b></font></a><b>:
                    750: </b><a href="plrbiaspar.txt"><b>plrbiaspar.txt</b></a></h5>
                    751: 
                    752: <pre>#Prevalence
                    753: #Age 1-1 2-2
                    754: 
                    755: #************ 
                    756: 70 0.90134 0.09866
                    757: 71 0.89177 0.10823 
                    758: 72 0.88139 0.11861 
                    759: 73 0.87015 0.12985 </pre>
1.4       lievre    760: 
1.6       lievre    761: <p>At age 70 the stationary prevalence is 0.90134 in state 1 and
1.3       lievre    762: 0.09866 in state 2. This stationary prevalence differs from
1.2       lievre    763: observed prevalence. Here is the point. The observed prevalence
                    764: at age 70 results from the incidence of disability, incidence of
                    765: recovery and mortality which occurred in the past of the cohort.
                    766: Stationary prevalence results from a simulation with actual
                    767: incidences and mortality (estimated from this cross-longitudinal
                    768: survey). It is the best predictive value of the prevalence in the
                    769: future if &quot;nothing changes in the future&quot;. This is
                    770: exactly what demographers do with a Life table. Life expectancy
                    771: is the expected mean time to survive if observed mortality rates
                    772: (incidence of mortality) &quot;remains constant&quot; in the
1.6       lievre    773: future. </p>
1.2       lievre    774: 
1.6       lievre    775: <h5><font color="#EC5E5E" size="3"><b>- Standard deviation of
                    776: stationary prevalence</b></font><b>: </b><a
                    777: href="vplrbiaspar.txt"><b>vplrbiaspar.txt</b></a></h5>
                    778: 
                    779: <p>The stationary prevalence has to be compared with the observed
1.2       lievre    780: prevalence by age. But both are statistical estimates and
                    781: subjected to stochastic errors due to the size of the sample, the
                    782: design of the survey, and, for the stationary prevalence to the
                    783: model used and fitted. It is possible to compute the standard
1.6       lievre    784: deviation of the stationary prevalence at each age.</p>
                    785: 
                    786: <h5><font color="#EC5E5E" size="3">-Observed and stationary
                    787: prevalence in state (2=disable) with the confident interval</font>:<b>
                    788: </b><a href="vbiaspar21.htm"><b>vbiaspar21.gif</b></a></h5>
                    789: 
                    790: <p>This graph exhibits the stationary prevalence in state (2)
                    791: with the confidence interval in red. The green curve is the
                    792: observed prevalence (or proportion of individuals in state (2)).
                    793: Without discussing the results (it is not the purpose here), we
                    794: observe that the green curve is rather below the stationary
                    795: prevalence. It suggests an increase of the disability prevalence
                    796: in the future.</p>
                    797: 
                    798: <p><img src="vbiaspar21.gif" width="400" height="300"></p>
                    799: 
                    800: <h5><font color="#EC5E5E" size="3"><b>-Convergence to the
                    801: stationary prevalence of disability</b></font><b>: </b><a
                    802: href="pbiaspar11.gif"><b>pbiaspar11.gif</b></a><br>
                    803: <img src="pbiaspar11.gif" width="400" height="300"> </h5>
1.2       lievre    804: 
1.6       lievre    805: <p>This graph plots the conditional transition probabilities from
                    806: an initial state (1=healthy in red at the bottom, or 2=disable in
1.2       lievre    807: green on top) at age <em>x </em>to the final state 2=disable<em> </em>at
                    808: age <em>x+h. </em>Conditional means at the condition to be alive
                    809: at age <em>x+h </em>which is <i>hP12x</i> + <em>hP22x</em>. The
                    810: curves <i>hP12x/(hP12x</i> + <em>hP22x) </em>and <i>hP22x/(hP12x</i>
                    811: + <em>hP22x) </em>converge with <em>h, </em>to the <em>stationary
                    812: prevalence of disability</em>. In order to get the stationary
                    813: prevalence at age 70 we should start the process at an earlier
                    814: age, i.e.50. If the disability state is defined by severe
                    815: disability criteria with only a few chance to recover, then the
                    816: incidence of recovery is low and the time to convergence is
1.6       lievre    817: probably longer. But we don't have experience yet.</p>
1.2       lievre    818: 
1.6       lievre    819: <h5><font color="#EC5E5E" size="3"><b>- Life expectancies by age
                    820: and initial health status</b></font><b>: </b><a
                    821: href="erbiaspar.txt"><b>erbiaspar.txt</b></a></h5>
                    822: 
                    823: <pre># Health expectancies 
                    824: # Age 1-1 1-2 2-1 2-2 
                    825: 70 10.9226 3.0401 5.6488 6.2122 
                    826: 71 10.4384 3.0461 5.2477 6.1599 
                    827: 72 9.9667 3.0502 4.8663 6.1025 
                    828: 73 9.5077 3.0524 4.5044 6.0401 </pre>
1.2       lievre    829: 
1.7       brouard   830: <pre>For example 70 10.4227 3.0402 5.6488 5.7123 means:
                    831: e11=10.4227 e12=3.0402 e21=5.6488 e22=5.7123</pre>
1.2       lievre    832: 
1.6       lievre    833: <pre><img src="expbiaspar21.gif" width="400" height="300"><img
                    834: src="expbiaspar11.gif" width="400" height="300"></pre>
1.2       lievre    835: 
1.6       lievre    836: <p>For example, life expectancy of a healthy individual at age 70
1.7       brouard   837: is 10.42 in the healthy state and 3.04 in the disability state
                    838: (=13.46 years). If he was disable at age 70, his life expectancy
                    839: will be shorter, 5.64 in the healthy state and 5.71 in the
                    840: disability state (=11.35 years). The total life expectancy is a
                    841: weighted mean of both, 13.46 and 11.35; weight is the proportion
1.2       lievre    842: of people disabled at age 70. In order to get a pure period index
1.6       lievre    843: (i.e. based only on incidences) we use the <a
                    844: href="#Stationary prevalence in each state">computed or
                    845: stationary prevalence</a> at age 70 (i.e. computed from
                    846: incidences at earlier ages) instead of the <a
                    847: href="#Observed prevalence in each state">observed prevalence</a>
                    848: (for example at first exam) (<a href="#Health expectancies">see
                    849: below</a>).</p>
                    850: 
                    851: <h5><font color="#EC5E5E" size="3"><b>- Variances of life
                    852: expectancies by age and initial health status</b></font><b>: </b><a
                    853: href="vrbiaspar.txt"><b>vrbiaspar.txt</b></a></h5>
                    854: 
                    855: <p>For example, the covariances of life expectancies Cov(ei,ej)
                    856: at age 50 are (line 3) </p>
                    857: 
                    858: <pre>   Cov(e1,e1)=0.4776  Cov(e1,e2)=0.0488=Cov(e2,e1)  Cov(e2,e2)=0.0424</pre>
                    859: 
                    860: <h5><font color="#EC5E5E" size="3"><b>- </b></font><a
                    861: name="Health expectancies"><font color="#EC5E5E" size="3"><b>Health
                    862: expectancies</b></font></a><font color="#EC5E5E" size="3"><b>
                    863: with standard errors in parentheses</b></font><b>: </b><a
                    864: href="trbiaspar.txt"><font face="Courier New"><b>trbiaspar.txt</b></font></a></h5>
                    865: 
                    866: <pre>#Total LEs with variances: e.. (std) e.1 (std) e.2 (std) </pre>
                    867: 
1.7       brouard   868: <pre>70 13.26 (0.22) 9.95 (0.20) 3.30 (0.14) </pre>
1.6       lievre    869: 
1.7       brouard   870: <p>Thus, at age 70 the total life expectancy, e..=13.26 years is
                    871: the weighted mean of e1.=13.46 and e2.=11.35 by the stationary
1.3       lievre    872: prevalence at age 70 which are 0.90134 in state 1 and 0.09866 in
1.7       brouard   873: state 2, respectively (the sum is equal to one). e.1=9.95 is the
1.2       lievre    874: Disability-free life expectancy at age 70 (it is again a weighted
1.7       brouard   875: mean of e11 and e21). e.2=3.30 is also the life expectancy at age
1.6       lievre    876: 70 to be spent in the disability state.</p>
1.2       lievre    877: 
1.6       lievre    878: <h5><font color="#EC5E5E" size="3"><b>-Total life expectancy by
                    879: age and health expectancies in states (1=healthy) and (2=disable)</b></font><b>:
                    880: </b><a href="ebiaspar1.gif"><b>ebiaspar1.gif</b></a></h5>
                    881: 
                    882: <p>This figure represents the health expectancies and the total
                    883: life expectancy with the confident interval in dashed curve. </p>
                    884: 
                    885: <pre>        <img src="ebiaspar1.gif" width="400" height="300"></pre>
                    886: 
                    887: <p>Standard deviations (obtained from the information matrix of
                    888: the model) of these quantities are very useful.
                    889: Cross-longitudinal surveys are costly and do not involve huge
                    890: samples, generally a few thousands; therefore it is very
                    891: important to have an idea of the standard deviation of our
                    892: estimates. It has been a big challenge to compute the Health
                    893: Expectancy standard deviations. Don't be confuse: life expectancy
                    894: is, as any expected value, the mean of a distribution; but here
                    895: we are not computing the standard deviation of the distribution,
                    896: but the standard deviation of the estimate of the mean.</p>
                    897: 
                    898: <p>Our health expectancies estimates vary according to the sample
                    899: size (and the standard deviations give confidence intervals of
                    900: the estimate) but also according to the model fitted. Let us
                    901: explain it in more details.</p>
                    902: 
                    903: <p>Choosing a model means ar least two kind of choices. First we
                    904: have to decide the number of disability states. Second we have to
                    905: design, within the logit model family, the model: variables,
                    906: covariables, confonding factors etc. to be included.</p>
                    907: 
                    908: <p>More disability states we have, better is our demographical
                    909: approach of the disability process, but smaller are the number of
1.2       lievre    910: transitions between each state and higher is the noise in the
                    911: measurement. We do not have enough experiments of the various
                    912: models to summarize the advantages and disadvantages, but it is
                    913: important to say that even if we had huge and unbiased samples,
                    914: the total life expectancy computed from a cross-longitudinal
                    915: survey, varies with the number of states. If we define only two
                    916: states, alive or dead, we find the usual life expectancy where it
                    917: is assumed that at each age, people are at the same risk to die.
                    918: If we are differentiating the alive state into healthy and
                    919: disable, and as the mortality from the disability state is higher
                    920: than the mortality from the healthy state, we are introducing
                    921: heterogeneity in the risk of dying. The total mortality at each
                    922: age is the weighted mean of the mortality in each state by the
                    923: prevalence in each state. Therefore if the proportion of people
                    924: at each age and in each state is different from the stationary
                    925: equilibrium, there is no reason to find the same total mortality
                    926: at a particular age. Life expectancy, even if it is a very useful
                    927: tool, has a very strong hypothesis of homogeneity of the
                    928: population. Our main purpose is not to measure differential
                    929: mortality but to measure the expected time in a healthy or
                    930: disability state in order to maximise the former and minimize the
                    931: latter. But the differential in mortality complexifies the
1.6       lievre    932: measurement.</p>
1.2       lievre    933: 
1.6       lievre    934: <p>Incidences of disability or recovery are not affected by the
                    935: number of states if these states are independant. But incidences
                    936: estimates are dependant on the specification of the model. More
                    937: covariates we added in the logit model better is the model, but
                    938: some covariates are not well measured, some are confounding
                    939: factors like in any statistical model. The procedure to &quot;fit
                    940: the best model' is similar to logistic regression which itself is
                    941: similar to regression analysis. We haven't yet been sofar because
                    942: we also have a severe limitation which is the speed of the
                    943: convergence. On a Pentium III, 500 MHz, even the simplest model,
                    944: estimated by month on 8,000 people may take 4 hours to converge.
                    945: Also, the program is not yet a statistical package, which permits
                    946: a simple writing of the variables and the model to take into
                    947: account in the maximisation. The actual program allows only to
                    948: add simple variables like age+sex or age+sex+ age*sex but will
                    949: never be general enough. But what is to remember, is that
1.2       lievre    950: incidences or probability of change from one state to another is
1.6       lievre    951: affected by the variables specified into the model.</p>
1.2       lievre    952: 
1.6       lievre    953: <p>Also, the age range of the people interviewed has a link with
                    954: the age range of the life expectancy which can be estimated by
1.2       lievre    955: extrapolation. If your sample ranges from age 70 to 95, you can
                    956: clearly estimate a life expectancy at age 70 and trust your
                    957: confidence interval which is mostly based on your sample size,
                    958: but if you want to estimate the life expectancy at age 50, you
                    959: should rely in your model, but fitting a logistic model on a age
1.6       lievre    960: range of 70-95 and estimating probabilties of transition out of
1.2       lievre    961: this age range, say at age 50 is very dangerous. At least you
                    962: should remember that the confidence interval given by the
                    963: standard deviation of the health expectancies, are under the
                    964: strong assumption that your model is the 'true model', which is
1.6       lievre    965: probably not the case.</p>
1.5       lievre    966: 
1.6       lievre    967: <h5><font color="#EC5E5E" size="3"><b>- Copy of the parameter
                    968: file</b></font><b>: </b><a href="orbiaspar.txt"><b>orbiaspar.txt</b></a></h5>
1.2       lievre    969: 
1.6       lievre    970: <p>This copy of the parameter file can be useful to re-run the
                    971: program while saving the old output files. </p>
1.2       lievre    972: 
1.6       lievre    973: <h5><font color="#EC5E5E" size="3"><b>- Prevalence forecasting</b></font><b>:
                    974: </b><a href="frbiaspar.txt"><b>frbiaspar.txt</b></a></h5>
1.2       lievre    975: 
1.7       brouard   976: <p
                    977: style="TEXT-ALIGN: justify; tab-stops: 45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt">First,
                    978: we have estimated the observed prevalence between 1/1/1984 and
                    979: 1/6/1988. The mean date of interview (weighed average of the
                    980: interviews performed between1/1/1984 and 1/6/1988) is estimated
                    981: to be 13/9/1985, as written on the top on the file. Then we
                    982: forecast the probability to be in each state. </p>
                    983: 
                    984: <p
                    985: style="TEXT-ALIGN: justify; tab-stops: 45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt">Example,
                    986: at date 1/1/1989 : </p>
                    987: 
                    988: <pre class="MsoNormal"># StartingAge FinalAge P.1 P.2 P.3
                    989: # Forecasting at date 1/1/1989
                    990:   73 0.807 0.078 0.115</pre>
                    991: 
                    992: <p
                    993: style="TEXT-ALIGN: justify; tab-stops: 45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt">Since
                    994: the minimum age is 70 on the 13/9/1985, the youngest forecasted
                    995: age is 73. This means that at age a person aged 70 at 13/9/1989
                    996: has a probability to enter state1 of 0.807 at age 73 on 1/1/1989.
                    997: Similarly, the probability to be in state 2 is 0.078 and the
                    998: probability to die is 0.115. Then, on the 1/1/1989, the
                    999: prevalence of disability at age 73 is estimated to be 0.088.</p>
1.4       lievre   1000: 
1.6       lievre   1001: <h5><font color="#EC5E5E" size="3"><b>- Population forecasting</b></font><b>:
                   1002: </b><a href="poprbiaspar.txt"><b>poprbiaspar.txt</b></a></h5>
1.4       lievre   1003: 
1.6       lievre   1004: <pre># Age P.1 P.2 P.3 [Population]
                   1005: # Forecasting at date 1/1/1989 
                   1006: 75 572685.22 83798.08 
                   1007: 74 621296.51 79767.99 
                   1008: 73 645857.70 69320.60 </pre>
1.4       lievre   1009: 
1.6       lievre   1010: <pre># Forecasting at date 1/1/19909 
                   1011: 76 442986.68 92721.14 120775.48
                   1012: 75 487781.02 91367.97 121915.51
                   1013: 74 512892.07 85003.47 117282.76 </pre>
1.4       lievre   1014: 
1.7       brouard  1015: <p>From the population file, we estimate the number of people in
                   1016: each state. At age 73, 645857 persons are in state 1 and 69320
                   1017: are in state 2. One year latter, 512892 are still in state 1,
                   1018: 85003 are in state 2 and 117282 died before 1/1/1990.</p>
                   1019: 
1.6       lievre   1020: <hr>
1.4       lievre   1021: 
1.8     ! lievre   1022: <h2><a name="example"></a><font color="#00006A">Trying an example</font></h2>
1.5       lievre   1023: 
1.6       lievre   1024: <p>Since you know how to run the program, it is time to test it
                   1025: on your own computer. Try for example on a parameter file named <a
                   1026: href="..\mytry\imachpar.txt">imachpar.txt</a> which is a copy of <font
                   1027: size="2" face="Courier New">mypar.txt</font> included in the
                   1028: subdirectory of imach, <font size="2" face="Courier New">mytry</font>.
                   1029: Edit it to change the name of the data file to <font size="2"
                   1030: face="Courier New">..\data\mydata.txt</font> if you don't want to
                   1031: copy it on the same directory. The file <font face="Courier New">mydata.txt</font>
                   1032: is a smaller file of 3,000 people but still with 4 waves. </p>
1.5       lievre   1033: 
1.6       lievre   1034: <p>Click on the imach.exe icon to open a window. Answer to the
                   1035: question:'<strong>Enter the parameter file name:'</strong></p>
1.5       lievre   1036: 
1.6       lievre   1037: <table border="1">
1.2       lievre   1038:     <tr>
1.7       brouard  1039:         <td width="100%"><strong>IMACH, Version 0.71</strong><p><strong>Enter
1.6       lievre   1040:         the parameter file name: ..\mytry\imachpar.txt</strong></p>
1.2       lievre   1041:         </td>
                   1042:     </tr>
                   1043: </table>
                   1044: 
1.6       lievre   1045: <p>Most of the data files or image files generated, will use the
1.2       lievre   1046: 'imachpar' string into their name. The running time is about 2-3
                   1047: minutes on a Pentium III. If the execution worked correctly, the
                   1048: outputs files are created in the current directory, and should be
1.6       lievre   1049: the same as the mypar files initially included in the directory <font
                   1050: size="2" face="Courier New">mytry</font>.</p>
1.5       lievre   1051: 
1.6       lievre   1052: <ul>
                   1053:     <li><pre><u>Output on the screen</u> The output screen looks like <a
                   1054: href="imachrun.LOG">this Log file</a>
                   1055: #
1.5       lievre   1056: 
1.6       lievre   1057: title=MLE datafile=..\data\mydata.txt lastobs=3000 firstpass=1 lastpass=3
                   1058: ftol=1.000000e-008 stepm=24 ncov=2 nlstate=2 ndeath=1 maxwav=4 mle=1 weight=0</pre>
                   1059:     </li>
                   1060:     <li><pre>Total number of individuals= 2965, Agemin = 70.00, Agemax= 100.92
1.5       lievre   1061: 
1.6       lievre   1062: Warning, no any valid information for:126 line=126
                   1063: Warning, no any valid information for:2307 line=2307
                   1064: Delay (in months) between two waves Min=21 Max=51 Mean=24.495826
                   1065: <font face="Times New Roman">These lines give some warnings on the data file and also some raw statistics on frequencies of transitions.</font>
                   1066: Age 70 1.=230 loss[1]=3.5% 2.=16 loss[2]=12.5% 1.=222 prev[1]=94.1% 2.=14
                   1067:  prev[2]=5.9% 1-1=8 11=200 12=7 13=15 2-1=2 21=6 22=7 23=1
                   1068: Age 102 1.=0 loss[1]=NaNQ% 2.=0 loss[2]=NaNQ% 1.=0 prev[1]=NaNQ% 2.=0 </pre>
                   1069:     </li>
                   1070: </ul>
1.2       lievre   1071: 
1.6       lievre   1072: <p>&nbsp;</p>
1.2       lievre   1073: 
1.6       lievre   1074: <ul>
                   1075:     <li>Maximisation with the Powell algorithm. 8 directions are
                   1076:         given corresponding to the 8 parameters. this can be
                   1077:         rather long to get convergence.<br>
                   1078:         <font size="1" face="Courier New"><br>
1.2       lievre   1079:         Powell iter=1 -2*LL=11531.405658264877 1 0.000000000000 2
                   1080:         0.000000000000 3<br>
                   1081:         0.000000000000 4 0.000000000000 5 0.000000000000 6
                   1082:         0.000000000000 7 <br>
                   1083:         0.000000000000 8 0.000000000000<br>
                   1084:         1..........2.................3..........4.................5.........<br>
                   1085:         6................7........8...............<br>
                   1086:         Powell iter=23 -2*LL=6744.954108371555 1 -12.967632334283
                   1087:         <br>
                   1088:         2 0.135136681033 3 -7.402109728262 4 0.067844593326 <br>
                   1089:         5 -0.673601538129 6 -0.006615504377 7 -5.051341616718 <br>
                   1090:         8 0.051272038506<br>
                   1091:         1..............2...........3..............4...........<br>
                   1092:         5..........6................7...........8.........<br>
                   1093:         #Number of iterations = 23, -2 Log likelihood =
                   1094:         6744.954042573691<br>
                   1095:         # Parameters<br>
                   1096:         12 -12.966061 0.135117 <br>
                   1097:         13 -7.401109 0.067831 <br>
                   1098:         21 -0.672648 -0.006627 <br>
1.6       lievre   1099:         23 -5.051297 0.051271 </font><br>
                   1100:         </li>
                   1101:     <li><pre><font size="2">Calculation of the hessian matrix. Wait...
                   1102: 12345678.12.13.14.15.16.17.18.23.24.25.26.27.28.34.35.36.37.38.45.46.47.48.56.57.58.67.68.78
                   1103: 
                   1104: Inverting the hessian to get the covariance matrix. Wait...
                   1105: 
                   1106: #Hessian matrix#
                   1107: 3.344e+002 2.708e+004 -4.586e+001 -3.806e+003 -1.577e+000 -1.313e+002 3.914e-001 3.166e+001 
                   1108: 2.708e+004 2.204e+006 -3.805e+003 -3.174e+005 -1.303e+002 -1.091e+004 2.967e+001 2.399e+003 
                   1109: -4.586e+001 -3.805e+003 4.044e+002 3.197e+004 2.431e-002 1.995e+000 1.783e-001 1.486e+001 
                   1110: -3.806e+003 -3.174e+005 3.197e+004 2.541e+006 2.436e+000 2.051e+002 1.483e+001 1.244e+003 
                   1111: -1.577e+000 -1.303e+002 2.431e-002 2.436e+000 1.093e+002 8.979e+003 -3.402e+001 -2.843e+003 
                   1112: -1.313e+002 -1.091e+004 1.995e+000 2.051e+002 8.979e+003 7.420e+005 -2.842e+003 -2.388e+005 
                   1113: 3.914e-001 2.967e+001 1.783e-001 1.483e+001 -3.402e+001 -2.842e+003 1.494e+002 1.251e+004 
                   1114: 3.166e+001 2.399e+003 1.486e+001 1.244e+003 -2.843e+003 -2.388e+005 1.251e+004 1.053e+006 
                   1115: # Scales
                   1116: 12 1.00000e-004 1.00000e-006
                   1117: 13 1.00000e-004 1.00000e-006
                   1118: 21 1.00000e-003 1.00000e-005
                   1119: 23 1.00000e-004 1.00000e-005
                   1120: # Covariance
                   1121:   1 5.90661e-001
                   1122:   2 -7.26732e-003 8.98810e-005
                   1123:   3 8.80177e-002 -1.12706e-003 5.15824e-001
                   1124:   4 -1.13082e-003 1.45267e-005 -6.50070e-003 8.23270e-005
                   1125:   5 9.31265e-003 -1.16106e-004 6.00210e-004 -8.04151e-006 1.75753e+000
                   1126:   6 -1.15664e-004 1.44850e-006 -7.79995e-006 1.04770e-007 -2.12929e-002 2.59422e-004
                   1127:   7 1.35103e-003 -1.75392e-005 -6.38237e-004 7.85424e-006 4.02601e-001 -4.86776e-003 1.32682e+000
                   1128:   8 -1.82421e-005 2.35811e-007 7.75503e-006 -9.58687e-008 -4.86589e-003 5.91641e-005 -1.57767e-002 1.88622e-004
                   1129: # agemin agemax for lifexpectancy, bage fage (if mle==0 ie no data nor Max likelihood).
                   1130: 
                   1131: 
                   1132: agemin=70 agemax=100 bage=50 fage=100
                   1133: Computing prevalence limit: result on file 'plrmypar.txt' 
                   1134: Computing pij: result on file 'pijrmypar.txt' 
                   1135: Computing Health Expectancies: result on file 'ermypar.txt' 
                   1136: Computing Variance-covariance of DFLEs: file 'vrmypar.txt' 
                   1137: Computing Total LEs with variances: file 'trmypar.txt' 
                   1138: Computing Variance-covariance of Prevalence limit: file 'vplrmypar.txt' 
                   1139: End of Imach
                   1140: </font></pre>
                   1141:     </li>
1.2       lievre   1142: </ul>
                   1143: 
1.6       lievre   1144: <p><font size="3">Once the running is finished, the program
                   1145: requires a caracter:</font></p>
1.2       lievre   1146: 
1.6       lievre   1147: <table border="1">
1.2       lievre   1148:     <tr>
1.6       lievre   1149:         <td width="100%"><strong>Type e to edit output files, c
                   1150:         to start again, and q for exiting:</strong></td>
1.2       lievre   1151:     </tr>
                   1152: </table>
                   1153: 
1.6       lievre   1154: <p><font size="3">First you should enter <strong>e </strong>to
                   1155: edit the master file mypar.htm. </font></p>
                   1156: 
                   1157: <ul>
                   1158:     <li><u>Outputs files</u> <br>
1.3       lievre   1159:         <br>
1.6       lievre   1160:         - Observed prevalence in each state: <a
                   1161:         href="..\mytry\prmypar.txt">pmypar.txt</a> <br>
                   1162:         - Estimated parameters and the covariance matrix: <a
                   1163:         href="..\mytry\rmypar.txt">rmypar.txt</a> <br>
                   1164:         - Stationary prevalence in each state: <a
                   1165:         href="..\mytry\plrmypar.txt">plrmypar.txt</a> <br>
                   1166:         - Transition probabilities: <a
                   1167:         href="..\mytry\pijrmypar.txt">pijrmypar.txt</a> <br>
                   1168:         - Copy of the parameter file: <a
                   1169:         href="..\mytry\ormypar.txt">ormypar.txt</a> <br>
                   1170:         - Life expectancies by age and initial health status: <a
                   1171:         href="..\mytry\ermypar.txt">ermypar.txt</a> <br>
1.2       lievre   1172:         - Variances of life expectancies by age and initial
1.6       lievre   1173:         health status: <a href="..\mytry\vrmypar.txt">vrmypar.txt</a>
1.2       lievre   1174:         <br>
1.6       lievre   1175:         - Health expectancies with their variances: <a
                   1176:         href="..\mytry\trmypar.txt">trmypar.txt</a> <br>
                   1177:         - Standard deviation of stationary prevalence: <a
                   1178:         href="..\mytry\vplrmypar.txt">vplrmypar.txt</a><br>
                   1179:         - Prevalences forecasting: <a href="frmypar.txt">frmypar.txt</a>
1.2       lievre   1180:         <br>
1.6       lievre   1181:         - Population forecasting (if popforecast=1): <a
                   1182:         href="poprmypar.txt">poprmypar.txt</a> <br>
                   1183:         </li>
                   1184:     <li><u>Graphs</u> <br>
1.2       lievre   1185:         <br>
1.6       lievre   1186:         -<a href="../mytry/pemypar1.gif">One-step transition
                   1187:         probabilities</a><br>
                   1188:         -<a href="../mytry/pmypar11.gif">Convergence to the
                   1189:         stationary prevalence</a><br>
                   1190:         -<a href="..\mytry\vmypar11.gif">Observed and stationary
                   1191:         prevalence in state (1) with the confident interval</a> <br>
                   1192:         -<a href="..\mytry\vmypar21.gif">Observed and stationary
                   1193:         prevalence in state (2) with the confident interval</a> <br>
                   1194:         -<a href="..\mytry\expmypar11.gif">Health life
                   1195:         expectancies by age and initial health state (1)</a> <br>
                   1196:         -<a href="..\mytry\expmypar21.gif">Health life
                   1197:         expectancies by age and initial health state (2)</a> <br>
                   1198:         -<a href="..\mytry\emypar1.gif">Total life expectancy by
                   1199:         age and health expectancies in states (1) and (2).</a> </li>
1.2       lievre   1200: </ul>
                   1201: 
1.6       lievre   1202: <p>This software have been partly granted by <a
                   1203: href="http://euroreves.ined.fr">Euro-REVES</a>, a concerted
1.2       lievre   1204: action from the European Union. It will be copyrighted
                   1205: identically to a GNU software product, i.e. program and software
                   1206: can be distributed freely for non commercial use. Sources are not
                   1207: widely distributed today. You can get them by asking us with a
1.6       lievre   1208: simple justification (name, email, institute) <a
                   1209: href="mailto:brouard@ined.fr">mailto:brouard@ined.fr</a> and <a
                   1210: href="mailto:lievre@ined.fr">mailto:lievre@ined.fr</a> .</p>
                   1211: 
1.7       brouard  1212: <p>Latest version (0.71a of March 2002) can be accessed at <a
1.8     ! lievre   1213: href="http://euroreves.ined.fr/imach">http://euroreves.ined.fr/imach</a><br>
1.6       lievre   1214: </p>
1.2       lievre   1215: </body>
                   1216: </html>

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