Educational differences in the prevalence of mobility disability in old age: the dynamics of incidence, mortality, and recovery.

OBJECTIVES: Older people with less education have substantially higher prevalence rates of mobility disability. This study aimed to establish the relative contributions of incidence, recovery rates, and death to prevalence differences in mobility disability associated with educational status. METHODS: Data were from 3 sites of the Established Populations for Epidemiological Study of the Elderly, covering 8,871 people aged 65-84 years who were followed for up to 7 years. Participants were classified on years of education received and as disabled if they needed help or were unable to walk up or down stairs or walk half a mile. A Markov model computed relative risks, adjusting for the effects of repeated observations on the same individuals. RESULTS: Differences between education groups in person-years lived with disability were large. The relative risk of incident disability in men with 0-7 years of education (vs. those with 12 or more years) was 1.65 (95% CI = 1.37-1.97) and in women was 1.70 (95% CI = 1.15-2.53). Both recovery risks and risks of death in those with disability were not significantly different across education groups in either gender. DISCUSSION: Higher incidence of disability is the main contributor to the substantially higher prevalence of disability in older people of lower socioeconomic status. Efforts to reduce the disparity in disability rates by socioeconomic status in old age should focus mainly on preventing disability, because differences in the course of mobility disability after onset appear to play a limited role in the observed prevalence disparities.

Estimating incidence of dementia subtypes: assessing the impact of missed cases.

In many community-based studies on the incidence of dementia, a target population is screened and a subsample is clinically evaluated at baseline and follow-up. Incidence rates are affected by missed cases at both exams and this complicates the estimation of these rates. Recent work proposes a regression-based technique for joint estimation of prevalence and incidence and suggests the use of surrogate information obtained on the entire cohort at both times to calculate the expected score equation contribution for individuals missing clinical exams at one or both times. This helps to quantify the impact of missed diagnosis upon the incidence estimates and their confidence intervals. We extend this work to the setting of subtypes of dementia for use in the Honolulu-Asia Aging Study on incidence of dementia. The technique is applied using two separate models for the effect of age on dementia incidence. Subsequently, shrinkage estimation methods are applied to provide more precise estimates of the rates. Published in 2000 by John Wiley & Sons, Ltd.

Active life expectancy from annual follow-up data with missing responses.

Active life expectancy (ALE) at a given age is defined as the expected remaining years free of disability. In this study, three categories of health status are defined according to the ability to perform activities of daily living independently. Several studies have used increment-decrement life tables to estimate ALE, without error analysis, from only a baseline and one follow-up interview. The present work conducts an individual-level covariate analysis using a three-state Markov chain model for multiple follow-up data. Using a logistic link, the model estimates single-year transition probabilities among states of health, accounting for missing interviews. This approach has the advantages of smoothing subsequent estimates and increased power by using all follow-ups. We compute ALE and total life expectancy from these estimated single-year transition probabilities. Variance estimates are computed using the delta method. Data from the Iowa Established Population for the Epidemiologic Study of the Elderly are used to test the effects of smoking on ALE on all 5-year age groups past 65 years, controlling for sex and education.

Association of vitamin E and C supplement use with cognitive function and dementia in elderly men.

OBJECTIVE: To determine whether use of vitamin E and C supplements protects against subsequent development of dementia and poor cognitive functioning. METHODS: The Honolulu-Asia Aging Study is a longitudinal study of Japanese-American men living in Hawaii. Data for this study were obtained from a subsample of the cohort interviewed in 1982, and from the entire cohort from a mailed questionnaire in 1988 and the dementia prevalence survey in 1991 to 1993. The subjects included 3,385 men, age 71 to 93 years, whose use of vitamin E and C supplements had been ascertained previously. Cognitive performance was assessed with the Cognitive Abilities Screening Instrument, and subjects were stratified into four groups: low, low normal, mid normal, and high normal. For the dementia analyses, subjects were divided into five mutually exclusive groups: AD (n = 47), vascular dementia (n = 35), mixed/other types of dementia (n = 50), low cognitive test scorers without diagnosed dementia (n = 254), and cognitively intact (n = 2,999; reference). RESULTS: In a multivariate model controlling for other factors, a significant protective effect was found for vascular dementia in men who had reported taking both vitamin E and C supplements in 1988 (odds ratio [OR], 0.12; 95% CI, 0.02 to 0.88). They were also protected against mixed/other dementia (OR, 0.31; 95% CI, 0.11 to 0.89). No protective effect was found for Alzheimer's dementia (OR, 1.81; 95% CI, 0.91 to 3.62). Among those without dementia, use of either vitamin E or C supplements alone in 1988 was associated significantly with better cognitive test performance at the 1991 to 1993 examination (OR, 1.25; 95% CI, 1.04 to 1.50), and use of both vitamin E and C together had borderline significance (OR, 1.18; 95% CI, 0.995 to 1.39). CONCLUSIONS: These results suggest that vitamin E and C supplements may protect against vascular dementia and may improve cognitive function in late life.

APOE-epsilon4 predicts incident AD in Japanese-American men: the honolulu-asia aging study.

The authors assessed the 3-year incidence of dementia, including subtypes, in 2,603 Japanese-American men 71 to 93 years of age who were dementia free at baseline. There were 137 new cases of dementia according to the Diagnostic and Statistical Manual of Mental Disorders, 3rd edition, revised, including 51 with a primary diagnosis of AD. The rates for all subtypes increased with age. Men with an APOE4 allele had a significantly increased risk of AD of 2.39 (95% CI, 1.07, 5.31), after adjusting for age and education. There was no significant relationship of APOE4 with other subtypes of dementia.

Sex differences in the prevalence of mobility disability in old age: the dynamics of incidence, recovery, and mortality.

OBJECTIVES: This study examined sex differences in the prevalence of mobility disability in older adults according to the influences of three components of prevalence: disability incidence, recovery from disability, and mortality. METHODS: Participants in a population-based study of older adults from three communities in the United States (N = 10,263) were studied for up to 7 years. Life table methods were used to estimate the influence of each of the three components of disability prevalence in women and men. Sex differences in probabilities for transition states were measured by relative risks derived from a single model using a Markov chain approach. RESULTS: The proportion of disabled women increased from 22% of women aged 70 years to 81% of those aged 90 years. In men, comparable figures were 15% and 57%. Incidence had the greatest impact on the sex differences in disability prevalence until age 90 and older when recovery rates had a greater impact on differences in prevalence. Mortality differences in men and women had only a modest impact on sex differences in disability prevalence. These findings initially seemed to contradict striking sex differences observed in the relative risks for mortality in men compared with women. Subsequent graphical analyses showed that incidence rather than recovery or mortality largely accounted for sex differences in disability prevalence in old age. CONCLUSION: Disability incidence, recovery from disability, and mortality dynamically influence the sex differences in the prevalence of mobility disability. However, incidence has the greatest impact overall on the higher prevalence of disability in women compared with men.

Incidence and remission of insomnia among elderly adults in a biracial cohort.

OBJECTIVES: To determine the incidence and remission rates of insomnia in older adults according to race and associated risk factors in a three-year longitudinal study. METHODS: 2,971 men and women, aged 65 years and older, completed questionnaires administered by trained interviewers at baseline and three years later. Data concerning difficulty falling asleep or early morning arousal (insomnia), along with self-reports of physical disability, respiratory symptoms, depressive symptomatology, perceived health status, and use of prescribed sedative medication, were collected and analyzed. RESULTS: Overall, 15% of the participants without symptoms of insomnia at baseline reported chronic difficulty falling asleep or early morning arousal three years later in follow-up interviews. African-American women had a significantly (p < 0.01) higher incidence of insomnia (19%) compared with African-American men (12%) or with white men and women (both 14%). Men were more likely than women to no longer report symptoms at follow-up (64% vs 42%; p < 0.01). For both races, the presence of depressed mood was a risk factor for the incidence of insomnia, and the absence of depressed mood was a predictor of remission. CONCLUSIONS: Insomnia occurs more frequently in African-American women than in African-American men or than in white men or women. Regardless of race, women are less likely than men to resolve their insomnia. The high prevalence and incidence of morbidity in elderly African-American women may contribute to their high rate of insomnia.

Smoking, physical activity, and active life expectancy.

The effect of smoking and physical activity on active and disabled life expectancy was estimated using data from the Established Populations for Epidemiologic Studies of the Elderly (EPESE). Population-based samples of persons aged > or = 65 years from the East Boston, Massachusetts, New Haven, Connecticut, and Iowa sites of the EPESE were assessed at baseline between 1981 and 1983 and followed for mortality and disability over six annual follow-ups. A total of 8,604 persons without disability at baseline were classified as "ever" or "never" smokers and doing "low," "moderate," or "high" level physical activity. Active and disabled life expectancies were estimated using a Markov chain model. Compared with smokers, men and women nonsmokers survived 1.6-3.9 and 1.6-3.6 years longer, respectively, depending on level of physical activity. When smokers were disabled and close to death, most nonsmokers were still nondisabled. Physical activity, from low to moderate to high, was significantly associated with more years of life expectancy in both smokers (9.5, 10.5, 12.9 years in men and 11.1, 12.6, 15.3 years in women at age 65) and nonsmokers (11.0, 14.4, 16.2 years in men and 12.7, 16.2, 18.4 years in women at age 65). Higher physical activity was associated with fewer years of disability prior to death. These findings provide strong and explicit evidence that refraining from smoking and doing regular physical activity predict a long and healthy life.

Evidence for a black-white crossover in all-cause and coronary heart disease mortality in an older population: the North Carolina EPESE.

OBJECTIVES: This cohort study evaluated racial differences in mortality among Blacks and Whites 65 years and older. METHODS: A total of 4136 men and women (1875 Whites and 2261 Blacks) living in North Carolina were interviewed in 1986 and followed up for mortality until 1994. Hazard ratios (HRs) for all-cause and cause-specific mortality were calculated, with adjustment for sociodemographic and coronary heart disease (CHD) risk factors. RESULTS: Black persons had higher mortality rates than Whites at young-old age (65-80 years) but had significantly lower mortality rates after age 80. Black persons age 80 or older had a significantly lower risk of all-cause mortality (HR of Blacks vs Whites, 0.75; 95% confidence interval [CI] = 0.62, 0.90) and of CHD mortality (HR 0.44: 95% CI = 0.30, 0.66). These differences were not observed for other causes of death. CONCLUSIONS: Racial differences in mortality are modified by age. This mortality crossover could be attributed to selective survival of the healthiest oldest Blacks or to other biomedical factors affecting longevity after age 80. Because the crossover was observed for CHD deaths only, age overreporting by Black older persons seems an unlikely explanation of the mortality differences.

Grip strength changes over 27 yr in Japanese-American men.

The aim of this study was to describe changes in grip strength over a follow-up period of approximately 27 yr and to study the associations of rate of strength decline with weight change and chronic conditions. The data are from the Honolulu Heart Program, a prospective population-based study established in 1965. Participants at exam 1 were 8,006 men (ages 45-68 yr) who were of Japanese ancestry and living in Hawaii. At follow-up, 3,741 men (age range, 71-96 yr) participated. Those who died before the follow-up showed significantly lower grip-strength values at baseline than did the survivors. The average annualized strength change among the survivors was -1.0%. Steeper decline (>1.5%/yr) was associated with older age at baseline, greater weight decrease, and chronic conditions such as stroke, diabetes, arthritis, coronary heart disease, and chronic obstructive pulmonary disease. The risk factors for having very low hand-grip strength at follow-up, here termed grip-strength disability (

Racial differences in muscle strength in disabled older women.

This study examines racial differences in muscle strength, and associations of muscle strength to level of physical activity and severity of disability, among a community sample of 254 black and 665 white, moderately to severely disabled women aged 65 and older. Potential confounders that were adjusted for in the models included age, body weight and height, joint pain, number of chronic conditions, and socioeconomic status. Hand grip, hip flexion, and knee extension forces were measured using portable hand-held dynamometers in the participants' homes. Hand grip strength was measured as the maximal isometric force. Hip flexion and knee extension forces were measured as the greatest force the tester had to apply to break the isometric contraction. A declining strength gradient was observed with increasing severity of disability and for decreasing level of physical activity in both races. At equal levels of disability or physical activity, blacks had better hand grip and hip flexion strength, but knee extension strength did not differ by race. The greater hand grip and hip flexion strength found in black women may be related to their greater muscle mass and known racial differences in body dimensions. No consistent racial differences were observed in the relationship between physical activity and muscle strength, or muscle strength and disability, suggesting that the role of muscle strength in the disablement process does not differ between races. Physical activity and exercise programs may be feasible ways to prevent worsening of disability in blacks and whites.

Association of muscle strength with maximum walking speed in disabled older women.

Our aim was to study the association of lower limb strength with maximum walking speed in disabled older women and to try to detect the reserve capacity threshold for maximum walking speed and the minimum strength required for walking at a speed of 1.22 m x s(-1), which is required in crossing signaled intersections. The data are from the baseline of Women's Health and Aging Study, a population-based study on causes and course of disability. Altogether, 1,002 disabled women participated in the tests, which took place at their homes. Maximum isometric hip flexion and knee extension forces were measured on both sides using a handheld dynamometer. For analytic purposes, knee extension torque/body mass ratio (KET/BM) was calculated. Maximum walking speed was measured with a stopwatch during a 4-m walk. KET/BM had a significant effect on walking speed after controlling for number of chronic conditions, balance, use of walking aid, joint pain, age, and body height and mass. A total of 42.3% of the variation in maximum walking speed was explained by these variables. The cumulative percentage distribution of KET/BM of those able to attain a maximum walking speed of 1.22 m x s(-1) (n = 148) was flat to the level of 1.1 N x m x kg(-1), after which it turned upward, indicating that the probability of attaining 1.22 m x s(-1) started to increase after that level. By using segmented linear regression analysis, 2.3 N x m x kg(-1) was found to be the cutoff point beyond which an increase in KET/BM did not correspond to an increase in maximum walking speed. Muscle strength was positively but not linearly associated with maximum walking speed. Strength testing may help to identify people close to functional thresholds and, thus, at risk of impaired walking, who would benefit most from strengthening exercises.

Analysis of contraceptive discontinuation in six developing countries from durations of use at survey.

We conduct a cross-national study of contraceptive discontinuation among currently married nonsterilized contracepting women in Bolivia, Egypt, Kenya, Sri Lanka, Thailand, and Zimbabwe using the Demographic and Health Surveys (DHS). Since the DHS contains no true completed epochs of contraceptive use, the distribution of use times at survey is used to approximate the distribution of the completed epochs using the renewal theorem. Two techniques based on this approximation are used. The first technique uses local linear regression smoothing of a histogram estimate of the use time at survey pdf which is converted into an estimate of the discontinuation probability function. The second technique poses a proportional hazards Weibull distribution for the discontinuation probability function which is then converted into a model for the use times at survey. This second technique is used to model the observed variations in use across countries while controlling for other sociodemographic factors such as children ever born, age, and education, as well as a variable which encodes knowledge of the fertility cycle. Pill discontinuation probabilities range from 0.12 to 0.47 in the first year. IUD discontinuation probabilities range from 0.18 to 0.53 in the first year. Discontinuation probabilities in Egypt over all methods are in agreement with those reported in Ali and Cleland (1995). Logged relative risks of pill discontinuation range from -0.94 (Sri Lanka) to 0 (Kenya), while logged relative risks of IUD discontinuation range from -0.53 (Sri Lanka) to 0.41 (Zimbabwe). The ordering of risks of pill discontinuation among the six countries considered is in agreement with the ordering of total fertility rates excerpted from Westoff (1991).