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1<?xml version="1.0" encoding="ISO-8859-1"?>
3<HTML_CONTENT xmlns:ibis="">
5        <ibis:doc>
6                <name>resource/LifeExp.xml</name>
7                <summary>Technical Notes</summary>
8                <description></description>
9                <author>Lois Haggard</author>
10                <company>New Mexico Department of Health</company>
11                <versions>
12                        <version><date>Sept 9, 2019</date><who>Maria</who><description>adapted for NJ</description></version>
13                        <version><date>Dec 24, 2012</date><who>Lois</who><description>created</description></version>
14                </versions>
15        </ibis:doc>
17        <TITLE>Life Expectancy</TITLE>
18        <CONTENT>
19                Click a bar to expand or collapse its content.
20                <br/><br/>
22                <ibis:ExpandableContent titleLevel="2"><SHOW/>
23                <TITLE>Definition</TITLE>
24                        <CONTENT>
25                                Life expectancy is the average expected number of years of life remaining from a given age, in a given population, according to the current mortality experience (age-specific death rates) of persons in the same population. Life expectancy is calculated from a table called a "Life Table." It is most often expressed as the life expectancy from birth, but is also commonly expressed as life expectancy from age 65.
26                        </CONTENT>
27                </ibis:ExpandableContent>
29                <ibis:ExpandableContent titleLevel="2"><HIDE/>
30                <TITLE>Types of Life Expectancy Calculation</TITLE>
31                        <CONTENT>
32                                Life expectancy calculation is based on a "life table," a table of numbers that calculates various
33                                elements for a set of age ranges. The distinctions between types of life expectancy calculation
34                                depend on the characteristics of the life table and the inputs to it.<br/><br/>
36                                <ibis:ExpandableContent titleLevel="5"><SHOW/>
37                                <TITLE>Cohort vs. Period Life Tables</TITLE>
38                                        <CONTENT>
39                                                <ul>
40                                                        <li>A cohort (or generation) life table uses data from a particular birth cohort, for example,
41                                                                the age-specific death rates for all persons born in 1900, after no persons remain alive
42                                                                in the group. (<a href="">Arias, 2019</a>)
43                                                        </li>
44                                                        <li>A period (or current) life table uses current death data, and represents what an hypothetical
45                                                                cohort would experience, given the mortality conditions in the current population. (<a href="">Arias, 2019</a>)
46                                                        </li>                                           
47                                                        <li>The current life table may be used to make statistical inferences and comparisons between the mortality
48                                                                experiences of different populations. (SEPHO, 2005)
49                                                        </li>
50                                                        <li><b>The life table that is calculated in the NJSHAD query system is calculated from a period life table.</b>
51                                                        </li>
52                                                </ul>
53                                        </CONTENT>
54                                </ibis:ExpandableContent>
56                                <ibis:ExpandableContent titleLevel="5"><SHOW/>
57                                <TITLE>Complete vs. Abridged Life Tables</TITLE>
58                                        <CONTENT>
59                                                <ul>
60                                                        <li>A complete life table calculates life expectancy for every single year of age.</li>
61                                                        <li>An abridged life table calculates life expectancy for grouped age intervals, typically 5- or 10-year age groups.</li> 
62                                                        <li>The abridged method is sometimes used when data are sparsely distributed by single years of age, or when single-year population estimates are not available to compute age-specific death rates. </li>
63                                                        <li><b>Life expectancy that is calculated in the NJSHAD query system is calculated from an abridged life table.</b></li>
64                                                </ul>
65                                                <br/>
66                                                Source: <a href="">Anderson, 1999</a>
67                                        </CONTENT>
68                                </ibis:ExpandableContent>
69                        </CONTENT>
70                </ibis:ExpandableContent>
72                <ibis:ExpandableContent titleLevel="2"><HIDE/>
73                <TITLE>Abridged Life Table</TITLE>
74                        <CONTENT>
75                                The life expectancy calculations in the NJSHAD <a href="query/selection/lifeexp/LifeExpSelection.html">
76                                Life Expectancy Query Module</a><!--, and in the example Life Table, below--> use a methodology developed by
77                                <a href="#Bib-2">Chiang (1968)</a>. This methodology was used because it was demonstrated to produce
78                                better estimates of life expectancy for small populations (SEPHO, 2005). The SEPHO
79                                report also demonstrated that  models with 5-year age bands to 85+ performed best, and that a population
80                                of 5,000 life years at risk produced an 'acceptable' 95% confidence interval of plus or minus 4 years of
81                                life expectancy.<br/><br/> 
83                                <h3>Sensitive to Infant Mortality</h3>
84                                        The calculation of life expectancy from birth is sensitive to infant mortality.
85                                        For that reason, life expectancy from age 65 is often used to compare populations.
86                                        <br/><br/>
88                                <h3>95% Confidence Interval</h3>
89                                        Calculation of 95% confidence interval for life expectancy is given in <a href="#Bib-2">Chiang (1984)</a>.
90                                        The variance of life expectancy (e) may be estimated as:<br/><br/>
92                                        <img src="contentfile/image/home/StdErrLifeExp.png" alt="Standard error for life expectancy"
93                                        title="Standard error for life expectancy"/><br/><br/>
95                                        Where the variance of quantity 'p' is:<br/><br/>
97                                        <img src="contentfile/image/home/Var_p.png" alt="Variance of quantity 'p'"
98                                        title="Variance of quantity 'p'"/>
99                                        <br/><br/>
100                                        Then, assuming that life expectancy is normally distributed, the 95% confidence interval is
101                                        found by multiplying the standard error by 1.96, where is standard error is the square root
102                                        of the variance of life expectancy (e).
103                                        <br/><br/>
105                                <h3>Programming a Life Expectancy Calculator in SAS for NJSHAD</h3>
106                                        A SAS program written by <a href="">Zdeb and Dairman (1997)</a> was adapted for use in
107                                        the NJSHAD <a href="query/selection/lifeexp/LifeExpSelection.html">Life Expectancy Query Module</a>.
109                        </CONTENT>
110                </ibis:ExpandableContent>
112                <ibis:ExpandableContent titleLevel="2"><HIDE/>
113                <TITLE>References</TITLE>
114                        <CONTENT>
115                                <p class="HRLeft"/>
116                                <a name="Bib-1"></a>1. Arias E, Xu JQ. <a href="">United States Life Tables, 2017</a>. National Vital Statistics Reports; vol 68 no 7. Hyattsville, MD: National Center for Health Statistics. 2019.
117                                <br/><br/>
119                                <a name="Bib-2"></a>2. SEPHO: South East Public Health Observatory. Technical Report: Calculating Life
120                                Expectancy in Small Areas. November 2005. ISBN 0-954-2971-4-8. Downloaded from
121                       on 12/24/2012.
122                                <br/><br/>             
124                                <a name="Bib-3"></a>3. Anderson RN. <a href="">Method for constructing complete annual U.S. life tables</a>. National Center for Health Statistics. Vital Health Stat 2(129). 1999.
125                                <br/><br/>
127                                <a name="Bib-4"></a>4. CL Chiang. The Life Table and Its Construction. In: Introduction to Stochastic
128                                Processes in Biostatistics. New York: John Wiley &amp; Sons, 1968:189-214. As cited in SEPHO, 2005.
129                                <br/><br/>             
131                                <a name="Bib-5"></a>5. CL Chiang. The Life Table and Its Applications. Malabar, Florida: Robert E.
132                                Krieger Publ. Co.; 1984. As cited in Association of Public Health Epidemiologists in Ontario, "10 Life
133                                Table Template V1.2." Downloaded from on 12/24/2012.
134                                <br/><br/>
136                                <a name="Bib-6"></a>6. Mike Zdeb and Matt Dairman, University at Albany-School of Public Health.
137                                Calculating and Illustrating the Probability of Developing Cancer Using SAS and SAS/Graph Software.
138                                SAS Users Group International Conference, March 16-19, 1997, San Diego, California; 1997. Downloaded
139                                from <a href=""></a> on 12/24/2012.
140                                <br/>
141                        </CONTENT>
142                </ibis:ExpandableContent>
144                <ibis:ExpandableContent titleLevel="2"><HIDE/>
145                <TITLE>For more information</TITLE>
146                        <CONTENT>
147                                National Center for Health Statistics, Life Tables: <a href=""></a>
148                        </CONTENT>
149                </ibis:ExpandableContent>
150        </CONTENT>
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