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Trends in Disability at Older Ages
Pages 1-28

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From page 1...
... By identifying the population eligible for existing programs and determining current program participation rates, information on trends in disability could improve the accuracy of projected costs of such pro grams. Identifying trends in disability is also required to evaluate health care reform measures that seek to expand home health care benefits.
From page 2...
... assess and compare findings from various studies of disability trends in the elderly population; (2) consider potential sources of bias that may explain differences in trencis from different surveys; (3)
From page 3...
... We begin with a discussion of prevalence trends; this is followed by an examination of trends in disability incidence; potential threats to validity and possible causes of observed trends are then discussed. Prevalence Disability prevalence refers to the proportion of a population with disability at a specific point in time.
From page 4...
... The National Long Term Care Survey The l 982, 1984, and 1989 NLTCS was clesignect to measure the prevalence and incidence of chronic disability in the U.S. elderly Medicare-enrolled population.
From page 5...
... All community residents in the sample were asked about their ADL and IADL limitations in 1982, 1984, and 1989; in addition, institutionalized sample members were asked about their ADL limitations in 1984 and 1989. Estimates of chronic disability prevalence from the 1982, 1984, and 1989 NLTCS are shown in s Table 1.
From page 6...
... Despite the absolute increases in the number of older persons with chronic disability, the proportion declined from 23.7 percent in 1982 to 22.6 percent in 1989 a decline of I.1 percentage points. There is some disagreement as to whether this change is occurring at all levels of chronic disability or mostly among people with chronic IADL disability.
From page 7...
... Nevertheless, the types of activities referred to as personal care activities ant} routine care activities are generally considered to be ADLs and IADLs, respectively. Thus, for purposes of this report, in order to facilitate comparisons across surveys, we use the terms ADL and IADL disability interchangeably with personal care and routine care limitations, respectively, when discussing the NHIS.
From page 8...
... Source: Feldmanetal.~1993~. Results inclicate a statistically significant decline in the proportion of the population with routine care limitations for most age groups; the relative number of those with personal care limitations, however, has not changed appreciably.
From page 9...
... Estimates have been adjusted using a combination of imputation and weighting procedures to account for sample attrition. Overall, We LSOA results indicate no consistent change in the prevalence of ADL or IADL disability over the six-year period.
From page 10...
... In most other cases, repeated cross-sectional surveys have been administered in the form of househoIct surveys. The primary source for international data on disability trends presented at the workshop is the United Nations Disability Statistics Data Base.
From page 11...
... Table 4 shows crucle prevalence rates of disability for the United States; Australia; Melton Mowbray, U.K.; and Manitoba, Canada. Estimates from the NLTCS represent the percentage of people with IADL or ADL disability or in an institution.
From page 12...
... Although variations in these surveys make comparisons across surveys nearly impossible, it nevertheless remains important to consider the experience of other countries when evaluating clisability trends in the United States. Summary of Findings Regarding Prevalence There is some evidence that IADL disability prevalence may have cleclined: although the LSOA shows no consistent pattern, data from the NLTCS show declines in the proportion of the elderly population with chronic IADL limitations, and the NHIS show cleclines in the prevalence of IADL limitations without regard to chronicity.
From page 13...
... Even if a cross-sectional survey includes questions on disability incidence during a previous period of time, only survivors would be captured by the survey. Thus, data from longitudinal surveys are required in which a sample of initially nondisabled persons is followed for a period of time.
From page 14...
... In addition, calculations employ the assumption that persons "aged-in" to the 1984 and 1989 samples were nondisabled at baseline; any misclassification with respect to disability of the aged-in sample biases incidence estimates in an upward direction, with the bias increasing over time. As a result, bias in the probability of maintaining functional status is in a negative direction (understating persistence)
From page 15...
... TABLE 6 Percentage of Initially Nondisabled Persons Experiencing a Decline in Functional Status: 1984-1990 LSOA (U.S. Population Aged 75+)
From page 16...
... According to the LSOA, the largest declines have occurred for those born prior to 1900 (aged 85 and older in l9X4~. Analysis: Potential Threats to Validity Overall, time series data from various sources indicate that there has been a recent decline in the prevalence of IADL disability and in the incidence of both IADL and ADL disability.
From page 17...
... Thus, the effect on prevalence trends of omitting long-stay hospital patients and institutionalizes} patients is likely to be small and in the direction of understating declines. Third, changes in the proportion of proxy respondents couict affect both prevalence and incidence trends if proxies report disability differently from study participants.
From page 18...
... Fifth, the use of longitudinal data can also influence prevalence trend estimates if only people with the most severe disability are selected into the sample; the trend will appear to improve due to the statistical phenomenon of regression to the mean. The LSOA is not vulnerable to this statistical artifact because it began in 1984 as a random sample of the noninstitutionalized elderly population.
From page 19...
... Such sources of bias could have opposite effects on trend estimates, with large losses to follow-up resulting in an overstatement of the decline in disability and shifts to proxy respondents dampening declines. Possible Causes of Observed Trends The existing data point to modest declines in the prevalence of IADL limitations and in the incidence of both IADL and ADL disability.
From page 20...
... Similarly, downward trencts in chronic disability, which in part rely on self-reports of expected length of disability, may reflect changes in respondents' perceptions about the future course of their clisability. FORECASTING DISABILITY Effective planning for medical, rehabilitative, and social services requires reliable estimates of me numbers and characteristics of current and future disabled people.
From page 21...
... Furthermore, disability is inherently a dynamic process in which function can decay or improve over time, even among those with the same underlying condition. Given the multiclimensional and dynamic nature of clisability, clear conceptual definitions are necessary to provide guidance in constructing operational definitions for forecasting models.
From page 22...
... Statistical Models The health of elderly populations can be projected using a number of different forecasting strategies, including actuarial, economic, demographic, and epidemiologic models (Manton, Singer, and Suzman, 1993~. In general, fecleral government programs have employed actuarial forecasting methods, which traclitionally have been used to anticipate the future fiscal risk of programs based on welldefined past experiences.
From page 23...
... In addition to anticipated changes in demographic conditions (most notably the aging of the baby boom generation) , other prominent 23 reasons accounting for the large increases in DI beneficiaries include unanticipated changes in economic conditions, programmatic policies and public outreach programs.
From page 24...
... Workshop participants also discussed the importance of enumerating an.d rleftqn~lin~ mn~l~.1 ~ ~ ~- ~-^~ A ~4 assumptions. Potential threats to external and internal validity are, for example, embedded in the construction of sampling weights, adjustments for sample design and attrition, and the use of proxy responses.
From page 25...
... Research on disability at older ages will continue to guide public policy makers. Surveys using questions tailored to existing programs can guide incremental program rule changes.
From page 26...
... Analysis of the National Long Term Care Survey shows that a smaller percentage of older persons had chronic difficulty performing IADL activities in 1989 than in 19X2. Findings from the National Health Interview Survey point to declines in the proportion of the older population with IADL disability for older men ant} women of all ages, with declines greatest at the oldest ages.
From page 27...
... Effective planning for medical, rehabilitation and social services requires reliable estimates of the numbers ant! characteristics of current ant!


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