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Biomedical subjects

K G Manton

Publications and source records attributed to K G Manton.

At least 37 records · Page 2Linked to original sources
PubMed1997

Changes in the age dependence of mortality and disability: cohort and other determinants.

Though the general trend in the United States has been toward increasing life expectancy both at birth and at age 65, the temporal rate of change in life expectancy since 1900 has been variable and often restricted to specific population groups. There have been periods during which the age- and gender-specific risks of particular causes of death have either increased or decreased. These periods partly reflect the persistent effects of population health factors on specific birth cohorts. It is important to understand the ebbs and flows of cause-specific mortality rates because general life expectancy trends are the product of interactions of multiple dynamic period and cohort factors. Consequently, we first review factors potentially affecting cohort health back to 1880 and explore how that history might affect the current and future cohort mortality risks of major chronic diseases. We then examine how those factors affect the age-specific linkage of disability and mortality in three sets of birth cohorts assessed using the 1982, 1984, and 1989 National Long Term Care Surveys and Medicare mortality data collected from 1982 to 1991. We find large changes in both mortality and disability in those cohorts, providing insights into what changes might have occurred and into what future changes might be expected.

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PubMed1997

Demographic trends for the aging female population.

Female life expectancy is higher at birth and at age 65 than the corresponding male life expectancies in the United States--and in most developed countries. In contrast, age-specific prevalences of chronic disability and institutional residence are higher for elderly women than for elderly men. This apparent contradiction results from the different morbid conditions causing chronic disability in US women and men. However, morbidity differentials do not explain all the gender differences in either disability or mortality. To test for general age-related factors causing female survival advantages, we analyzed male and female mortality and disability data from national longitudinal surveys of the health and functional status of elderly men and women from 1982, 1984, and 1989. Gender-specific mortality functions and models of disability changes were used to construct male and female cohort life tables where mortality and disability interact over the life of the modeled population. Even in populations where observation started 15 years after menopause, there were significant gender differences in the rate of aging estimated conditionally on chronic disability. Possible causes of gender differences in late-age mortality and their implications for the future health of the US female population are discussed.

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PubMed1996

Apolipoprotein E genotype determines survival in the oldest old (85 years or older) who have good cognition.

OBJECTIVE: To quantify the influence of apolipoprotein E (APOE) polymorphism on cognition and survival in a population sample aged 75 years or older. DESIGN: The Kungsholmen Project established a cohort of 1810 residents in a district in Stockholm, Sweden, aged 75 years or older in 1987. Information on cognition at cohort inception is available for all subjects. Subjects were followed up for mortality to January 1, 1995. SUBJECTS: Included in this study are 1077 subjects (of 1124 genotyped for APOE) with the common epsilon 2/3, epsilon 3/3, and epsilon 3/4 APOE genotypes. RESULTS: The odds of cognitive impairment for the epsilon 3/4 vs epsilon 3/3 genotype declined with age: 4.8 for age 75 through 79 years; 1.7 for age 80 through 84 years; and 1.0 (i.e., no association) for age 85 years or older. Despite this association, APOE polymorphism did not significantly predict survival in subjects younger than 85 years, nor did it predict survival in subjects 85 years or older who were cognitively impaired. Instead, survival varied fourfold with respect to APOE polymorphism in those 85 years or older who had good cognition: Mortality in subjects with the epsilon 2/3 genotype was half that in those who carried the epsilon 3/3 genotype (hazard ratio, 0.5; 95% confidence interval, 0.2 to 0.9), and mortality in subjects with the epsilon 3/4 genotype was twice that in those who carried the epsilon 3/3 genotype (hazard ratio, 2.0; 95% confidence interval, 1.1 to 3.5). This fourfold variation resulted in 2-year differences in survival. CONCLUSIONS: The minor sequence variation in the apolipoprotein E isoforms resulted in a fourfold difference in the risk of death among the oldest old (age > or = 85 years) with good cognition. The observed variation in mortality was unlikely to have been caused by cognitive impairment, as APOE polymorphism was not a risk factor for cognitive impairment in this age group.

Age Factors↗
PubMed1996

Proxy response patterns among the aged: effects on estimates of health status and medical care utilization from the 1982-1984 long-term care surveys.

We examined the use of proxies in samples of persons aged 65 years and over from the 1982 and 1984 National Long-Term Care Surveys (NLTCS). The NLTCS are designed to describe the Medicare-enrolled elderly population, their health and functioning, hospital, home health, and institutional use. The NLTCS, being longitudinal, allows trends in functional and health status to be examined as well as the changing character of community-based and institutional services used by chronically disabled persons aged 65 years and older. In analyses of proxy responses there was little evidence of differences in accuracy between self- and proxy reports in persons with different health and functional characteristics. The amount and type of proxy reporting did depend on the health and functional characteristics of the sample person. The cognitively impaired, and the frail elderly, had high levels of proxy use as well as small differences in the accuracy of reporting service use and program enrollment. The results are consistent with methodological studies of proxy reporting in health surveys of other populations.

Aged↗
PubMed1996

Longevity in the united states: age and sex-specific evidence on life span limits from mortality patterns 1960-1990.

Determining the biological limits to human longevity is more difficult than for most other species because humans are long-lived. Consequently, mortality data, such as from the U.S. vital statistics system, which have been available for a long time (relative to most epidemiological studies) and have large numbers of cases, including deaths reported to advanced ages, are important in studying human longevity-though care must be exercised in dealing with error in age reporting. Furthermore, it is unlikely that free-living humans can realize as much of their biological endowment for longevity as animals living in a highly controlled experimental environment. We examined changes, 1960 to 1990, in U.S. White male and female extinct cohort life tables and age at death distributions to (a) examine evidence for the effects of a biological life span limit in current U.S. mortality patterns and (b) produce lower bound estimates of that limit.

Aged↗
PubMed1996

Apolipoprotein E polymorphism and stroke in a population sample aged 75 years or more.

BACKGROUND AND PURPOSE: We investigated apolipoprotein E polymorphism stroke risk in a population sample of 1810 persons aged 75 years or more in Stockholm (the Kungsholmen Project). Information on cognition at cohort inception (from 1987 to 1989) and on stroke occurrence (from 1969 to 1994) is available for the cohort. In the cohort, cognitive impairment is associated with the epsilon 4 allele, and longer survival in subjects aged > or = 85 years with good cognition is associated with the epsilon 2 allele and the absence of epsilon 4. METHODS: We compared stroke incidence in the 1077 of 1124 genotyped subjects who carried epsilon 2/3, epsilon 3/3, or epsilon 3/4 and estimated the proportion of cognitive impairment attributable to stroke. RESULTS: Risk of stroke did not vary with apolipoprotein E polymorphism (P = .82): 24% of 87 incident stroke patients during follow-up compared with 25% of 827 subjects with normal cognition and no stroke diagnosis at baseline carried the epsilon 3/4 genotype. An estimated 9% of cognitive impairment was attributable to stroke. Notably, a reduced epsilon 3/4 frequency of 20% was found in subjects who survived a prior stroke and were included in the cohort, and risk of hemorrhagic stroke tended to be associated with the presence of the epsilon 3/4 genotype and the absence of epsilon 2/3. CONCLUSIONS: This population-based study indicates that apolipoprotein E polymorphism is not a risk factor for ischemic stroke in subjects aged > or = 75 years (although it might possibly influence survival after stroke occurrence and be a risk factor for infrequent hemorrhagic stroke) and that approximately 10% of cognitive impairment in this age group is attributable to stroke.

Aged↗
PubMed1996

Prior and current costs in capitated health plans: the effects of health status at enrollment.

We compared the prior and current costs of persons age 65 and older enrolling in a Social/Health Maintenance Organization in each of four sites with samples of persons using standard Medicare benefits in each site. Analyses were adjusted for individual health differences using case mix scores. Costs were examined in the year before S/HMO enrollment or prior to the sampling of a person using regular Medicare services as well as costs during the study. Costs during the study are analyzed using a two-stage procedure where first the propensity to enroll in a S/HMO is modeled and then costs derived from either Medicare sources or shadow prices assigned to service units provided in a S/HMO are modeled. The costs for case mix groups with different health and functional characteristics varied significantly. Cost differences between case mix classes differed between the S/HMO and FFS populations.

Aged↗
PubMed1996

Changes in health, mortality, and disability and their impact on long-term care needs.

The need for long-term care is driven both by the growth of the elderly population and changes in the age relations of morbidity, disability, and mortality. Data show these relations changed in the U.S. elderly population from 1982 to 1989. Chronic disability prevalence declined between the 1982 and 1989 U.S. National Long Term Care Surveys. Among those impaired, many persons using personal assistance to meet their needs shifted to the use of assisted housing and special equipment. The relation of these trends to other changes--such as the increasing educational level of the elderly population--is examined to estimate how future changes in disability and morbidity may affect the demand for long-term care. Disabilities at specific times as well as their transition rates were examined to determine how long individuals need long-term care. The analyses suggest that, while the amount of long-term care services needed will increase rapidly, the types and amounts of services used by the U.S. elderly population will undergo significant change.

Aged↗
PubMed1995

Survival after the age of 80 in the United States, Sweden, France, England, and Japan.

BACKGROUND: In many developed countries, life expectancy at birth is higher than in the United States. Newly available data permit, for the first time, reliable cross-national comparisons of mortality among persons 80 years of age or older. Such comparisons are important, because in many developed countries more than half of women and a third of men now die after the age of 80. METHODS: We used extinct-cohort methods to assess mortality in Japan, Sweden, France, and England (including Wales) and among U.S. whites for cohorts born from 1880 to 1894, and used cross-sectional data for the year 1987. Extinct-cohort methods rely on continuously collected data from death certificates and do not use the less reliable data from censuses. RESULTS: In the United States, life expectancy at the age of 80 and survival from the ages of 80 to 100 significantly exceeded life expectancy in Sweden, France, England, and Japan (P < 0.01). This finding was confirmed with accurate cross-sectional data for 1987. The average life expectancy in the United States is 9.1 years for 80-year-old white women and 7.0 years for 80-year-old white men. CONCLUSIONS: For people 80 years old or older, life expectancy is greater in the United States than it is in Sweden, France, England, and Japan. This finding suggests that elderly Americans are receiving better health care than the elderly citizens of other developed countries.

Aged↗
PubMed1995

The effects of health histories on stochastic process models of aging and mortality.

A model of human health history and aging, based on a multivariate stochastic process with both continuous diffusion and discrete jump components, is presented. Discrete changes generate non-Gaussian diffusion with time varying continuous state distributions. An approach to calculating transition rates in dynamically heterogeneous populations, which generalizes the conditional averaging of hazard rates done in "fixed frailty" population models, is presented to describe health processes with multiple jumps. Conditional semi-invariants are used to approximate the conditional p.d.f. of the unobserved health history components. This is useful in analyzing the age dependence of mortality and health changes at advanced age (e.g., 95+) where homeostatic controls weaken, and physiological dynamics and survival manifest nonlinear behavior.

Aging↗
PubMed1995

Nursing home residents: a multivariate analysis of their medical, behavioral, psychosocial, and service use characteristics.

BACKGROUND: Elderly residents of nursing homes often have multiple comorbidities and functional limitations. The status of 4,525 residents of complex and standard care units in 177 nursing homes where the nursing home was determined to provide adequate care, and from 14 specialized Alzheimer's units, was evaluated on 111 measures of medical condition, functional status, psychological well-being and cognitive performance in a demonstration study assessing quality of care in six states. Detailed measurements were also made of the types and amounts of services used (in minutes per day) by the residents. METHODS: Given the number of health measures, and the possibility of assessment error, a multivariate analytic procedure called Grade of Membership (GoM) was used. This procedure identified profiles of health and functioning measures to identify the characteristics of clinically distinct groups of nursing home residents. RESULTS: The analysis identified 11 profiles of health and functioning characteristics which described the 111 resident measurements. The 11 profiles predicted differentials in nursing home length of stay, and service use by various classes of caregivers. The GoM profiles described the data better than several other classification procedures applied to the same data. CONCLUSIONS: In nursing homes, elderly and oldest-old residents often have multiple comorbidities and disabilities. A multivariate procedure was able to identify the fundamental dimensions describing residents' variation on a number of health measures. These profiles predicted differences in service use so they had predictive validity. Thus, multivariate procedures may help identify clinically distinct groups in studies where complex measures are made.

Aged↗
PubMed1995

Changes in morbidity and chronic disability in the U.S. elderly population: evidence from the 1982, 1984, and 1989 National Long Term Care Surveys.

We examined changes in the reported prevalence of 16 medical conditions in the U.S. population age 65 and above using data from the 1982, 1984, and 1989 National Long Term Care Surveys. Changes in those disease prevalence rates were examined both as observed, and after standardizing for changes in the age, sex, and disability distributions in the U.S. elderly population between 1982 and 1989. We found significant declines in the net prevalence of the 16 medical conditions between 1982 and 1989. Significant changes were found in different disability, age, and gender groups and after standardizing for declines in disability in addition to age and sex. The declines in morbidity reported between 1982 and 1989 are consistent with the declines reported in the 1982 and 1989 National Long Term Care Surveys in the age and sex standardized prevalence of chronic disability and institutionalization.

Age Distribution↗
PubMed1995

Sex differences in human mortality and aging at late ages: the effect of mortality selection and state dynamics.

Models of gender differences in human mortality and aging depend on assumptions about temporal rates of physiological change. Simple models like the Gompertz fail to describe the mortality of either males or females at late ages. This suggests a need for biologically more detailed models to represent the age dependency of human mortality as well as gender differences in that age dependence. By modeling the sex-specific interaction of time-varying covariates with multiple dimensions of mortality selection, one can more accurately describe the age dependence of mortality and more complex physiological aging patterns. The multivariate model of aging changes is used to describe gender differences using data from (a) a longitudinal study of physiological changes and mortality and (b) a nationally representative longitudinal survey of changes in function and mortality.

Adult↗
PubMed1995

Evaluating long-term care demonstrations in real time with study design and plan performance interactions.

The evaluation of long-term care demonstrations has to deal with complex organizational entities, with large, heterogeneous client populations that, during the course of study, may have to change features of their organization or operation. The implications of such "real-time" changes are discussed for analyses of the operation and performance of Social/Health Maintenance Organizations over a 5-year period (2 years of start-up and enrollment and 3 years of follow-up). Analyses conducted of the plans in the context of real-time changes have to be based on different statistical models than for classic experimental study designs, where treatment factors are fixed rather than dynamic. A number of issues that may arise are identified, and possible approaches to their solutions described. Key words: long-term care; demonstrations; evaluations; study design; capitation.

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PubMed1994

Symptom profiles of psychiatric disorders based on graded disease classes: an illustration using data from the WHO International Pilot Study of Schizophrenia.

The Grade of Membership (GoM) model is a classification procedure which allows a person to be a member of more than one diagnostic class. It simultaneously quantifies the degrees of membership in classes while generating the discrete symptom profiles or 'pure types' describing classes. The model was applied to the symptomatology, history, and follow-up of 1065 cases in the WHO International Pilot Study of Schizophrenia. The model produced an eight diagnostic class or 'pure type' solution, of which five were related to the diagnostic concepts of schizophrenia and paranoid disorder, two types were affective disorders, and one asymptomatic type. A subtype of paranoid schizophreniform disorder found primarily in developing countries was identified. There was a strong association between pure types and the original clinical and computer generated (CATEGO) diagnoses. A GoM based psychiatric classification might more clearly identify core disease processes than conventional classification models by filtering the confounding effects of individual heterogeneity from pure type definitions.

Adult↗
PubMed1994

Time-varying covariates in models of human mortality and aging: multidimensional generalizations of the Gompertz.

Models of mortality and aging depend on assumptions about physiological change even if they are not made explicit. Standard models, like the Gompertz, often fail to describe mortality at extreme ages, suggesting a need for biologically more detailed and flexible models. One solution is to model the interaction of time-varying covariates with mortality to better describe the age dependence of mortality, test hypotheses about the relation of physiological change and mortality, and use longitudinal data to generalize assumptions about physiological change. This model is applied to (a) a 34-year follow-up of risk factors and mortality and (b) a 9.5-year follow-up of function and mortality from longitudinal surveys of the U.S. elderly population.

Adult↗
PubMed1994

A method for adjusting capitation payments to managed care plans using multivariate patterns of health and functioning: the experience of Social/Health Maintenance Organizations.

A multivariate procedure for identifying case-mix dimensions from discrete health variables is presented. Since the dimensions are generated only from health use data and not service use data, they can be used for adjust capitation rates to provide incentives to treat persons not currently well integrated in standard health care system (e.g., very ill persons, the uninsured) or to promote specific health outcomes. The procedure is illustrated with data from Social/Health Maintenance Organizations (S/HMO) since they provide both acute and long-term care (LTC) services. Thus, case-mix measures to adjust S/HMO reimbursements have to represent both medical conditions and the degree, and type, of functional impairment. From 31 health and functioning items, six case-mix dimensions, and scores for individuals on each, were calculated. The multivariate distribution of scores in S/HMO enrollees, and in Medicare eligible, comparison samples, were examined in each site to see how their health differed. S/HMO enrollees were healthier and less frail than persons remaining in the Medicare FFS system. Such differences are important in adjusting capitation rates to provide incentive to accept clients with complex health problems.

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