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Biomedical subjects

K G Manton

Publications and source records attributed to K G Manton.

At least 73 records · Page 4Linked to original sources
PubMed1991

Rectangularization of the survival curve: implications of an ill-posed question.

There has been considerable interest in the question of whether the human survival curve is becoming more rectangular as life expectancy in developed countries increases. However, despite the intuitive appeal of the rectangularization concept it has not been translated into a formally stated hypothesis about the shape of the human survival curve. This article examines how the hypothesis of rectangularization can be formally stated and the implications of that formalization for research on health and functional changes at later ages.

Aged↗
PubMed1991

Assessment of spatial variation of risks in small populations.

Often environmental hazards are assessed by examining the spatial variation of disease-specific mortality or morbidity rates. These rates, when estimated for small local populations, can have a high degree of random variation or uncertainty associated with them. If those rate estimates are used to prioritize environmental clean-up actions or to allocate resources, then those decisions may be influenced by this high degree of uncertainty. Unfortunately, the effect of this uncertainty is not to add "random noise" into the decision-making process, but to systematically bias action toward the smallest populations where uncertainty is greatest and where extreme high and low rate deviations are most likely to be manifest by chance. We present a statistical procedure for adjusting rate estimates for differences in variability due to differentials in local area population sizes. Such adjustments produce rate estimates for areas that have better properties than the unadjusted rates for use in making statistically based decisions about the entire set of areas. Examples are provided for county variation in bladder, stomach, and lung cancer mortality rates for U.S. white males for the period 1970 to 1979.

Bias↗
PubMed1991

The dynamics of population aging: demography and policy analysis.

The dynamics of population aging will broadly shape future social and economic conditions in the United States and in many other developed countries. Although the quantitative dimension of population aging is easily characterized, the associated forces producing changes in health and functioning among individuals are less well understood. For 14 years the Milbank Quarterly, under the editorship of David Willis, fostered research into the interaction of demographic, epidemiological, public health, and clinical factors in order better to understand population aging. The Quarterly spurred the collection of longitudinal data, based on representative samples of the U.S. elderly and oldest-old populations, which were crucial to efforts to answer critical questions about anticipated changes in health and functional status as the population ages. This research will give us a better grasp of the policy and service implications of an aging population.

Activities of Daily Living↗
PubMed1991

Multivariate procedures to describe clinical staging of melanoma.

Analyzing multivariate clinical data to identify subclasses of patients being treated for a specific disease may improve patient management and increase understanding of the behavior of disease under clinical conditions. In some cases, patients have been classified on prognostic characteristics using standard risk assessment procedures (e.g., Cox' regression). This requires long term follow-up, differentiates patients only on attributes relevant to survival, and assumes that patients are sampled from a common population. Other approaches involve the use of clustering algorithms to classify patients into categories based on multiple clinical attributes. We illustrate the use of a multivariate statistical procedure to directly characterize patients on multiple clinical characteristics. The procedure is designed to analyze discrete response data with parameters representing individual differences within groups. Its use is illustrated for patients with Stage I melanoma in determining how age is related to treatment response in different patient groups.

Adult↗
PubMed1990

Forecasting chronic disease risks in developing countries.

Declining fertility and infant mortality has caused the population in many developing countries to age. Population ageing can produce a rapid shift in the predominant public health problems from infant mortality and infectious diseases to chronic disease mortality at later ages. Designing public health strategies to deal with the health consequences of population ageing in developing countries is difficult both because of a remaining burden of infectious diseases and because of changes in life style associated with economic development that may raise chronic disease risks. Because there are few longitudinal studies of chronic disease risks in developing countries, we investigate the use of a planning and forecasting model, which combines data from multiple sources, in six developing countries.

Adolescent↗
PubMed1990

Changes in health service use and mortality among U.S. elderly in 1980-1986.

Concern has emerged about the impact on quality of care of recent changes in Medicare reimbursement for acute hospital episodes (i.e., the introduction of the Prospective Payment System based on the Diagnosis Related Groups Reimbursement methodology). One aspect of those concerns is that very sick patients would be prematurely discharged to nursing homes in which the high level of medical care required would not be available. This was recently studied in terms of changes between 1981 and 1985 in the location of deaths (e.g., hospital, institutional) reported on U.S. death certificates. We analyzed the death certificate data for a longer period of time (1980 to 1986) and stratified the analysis by both age and cause of death--which we felt were important determinants of location of death. We also examined data from the 1982 and 1984 National Long Term Care Surveys linked to data on Medicare service use. In those analyses we could explicitly identify chronically disabled and institutionalized populations and study death rates in different locations within those populations. Our analyses showed little evidence of increased mortality rates due to premature hospital discharge. There were, however, significant changes in the patterns of service use. More home health agency (HHA) and skilled nursing facility (SNF) services were consumed though the rates of death per episode in those venues declined.

Aged↗
PubMed1990

Functionally and medically defined subgroups of nursing home populations.

The functional and health characteristics of nursing home residents in New York State using a multivariate classification procedure are examined in this article. This analysis suggested that these characteristics could be explained in terms of six dimensions. The association of these six dimensions with two existing sets of nursing home case-mix groups was analyzed in order to determine how groups based only on the health and functional characteristics of residents related to groups based primarily on measures of current service use. A number of resident characteristics were not described well by case-mix measures based only on service use, suggesting the need to modify such groups using additional sources of input.

Activities of Daily Living↗
PubMed1990

Recent changes in service use patterns of disabled Medicare beneficiaries.

An analysis was made of the pre- and post-patterns of Medicare Part A service use using the samples of the 1982 and 1984 National Long-Term Care Surveys linked to the Medicare Part A bill files and mortality reports. The analysis was conducted both for the total elderly Medicare beneficiary population and for the community resident disabled population--a group felt to be particularly vulnerable to any adverse effect of the prospective payment system's induced change in service use. The expected changes in Medicare service patterns were identified, but there was no evidence of adverse changes in outcome--even for select vulnerable populations.

Aged↗
PubMed1990

Morbidity, disability, and long-term care of the elderly: implications for insurance financing.

A scarcity of empirical information to specify appropriate provisions and base rates for coverage has hindered the development of long-term-care (LTC) insurance. Data from three nationally representative surveys on the prevalence of morbidity and functional limitations among the elderly population suggest that health status among older Americans is highly dynamic, especially at higher disability levels. The bioactuarial data may help insurers define potential markets of purchasers of policies, and identify the numbers of persons with disabilities severe enough to trigger use of benefits. If the accuracy of individual service predictions could be increased further, reserve requirements and overall costs to LTC insurance carriers might be reduced.

Aged↗
PubMed1989

The propagation of uncertainty in human mortality processes operating in stochastic environments.

This paper presents a model describing how the uncertainty due to influential exogenous processes combines with stochasticity intrinsic to physiological aging processes and propagates through time to generate uncertainty about the future physiological state of the population. Variance expressions are derived for (a) the future values of the physiological variables under the assumption that external factors evolve under a linear stochastic diffusion process, and (b) the cohort survival functions and cohort life expectancies which reflect the uncertainty in the future values of the physiological variables. The model implies that a major component of uncertainty in forecasts of the physiological characteristics of a closed cohort is due to differential rates of survival associated with different realizations of the external process. This suggests that the limits to forecasting may be different in physiological systems subject to systematic mortality than in physical systems such as weather where the concepts of closed cohorts and of mortality selection have no simple analog.

Aging↗
PubMed1989

Empirical Bayes procedures for stabilizing maps of U.S. cancer mortality rates.

"The geographic mapping of age-standardized, cause-specific death rates is a powerful tool for identifying possible etiologic factors, because the spatial distribution of mortality risks can be examined for correlations with the spatial distribution of disease-specific risk factors. This article presents a two-stage empirical Bayes procedure for calculating age-standardized cancer death rates, for use in mapping, which are adjusted for the stochasticity of rates in small area populations. Using the adjusted rates helps isolate and identify spatial patterns in the rates. The model is applied to sex-specific data on U.S. county cancer mortality in the white population for 15 cancer sites for three decades: 1950-1959, 1960-1969, and 1970-1979. Selected results are presented as maps of county death rates for white males."

Age Factors↗
PubMed1989

The effect of nursing home use on Medicaid eligibility.

Presented are results of a descriptive analysis of the effects of nursing home use on Medicaid eligibility status. Data from the 1982 and 1984 National Long-Term Care Surveys were used to track a cohort of disabled elderly persons residing in the community in 1982 over the 2 years that followed. Although 12% spent some time in nursing homes between 1982 and 1984, about 40% was for short stays. In contrast to persons who did not use nursing homes, persons who entered nursing homes had a 4- to 5-fold risk of spending down to Medicaid eligibility.

Aged↗
PubMed1989

Controlling risk in capitation payment. Multivariate definitions of risk groups.

There are a number of different reimbursement strategies proposed for health maintenance organization (HMO) style health care providers. Each of those strategies is designed to leave the provider at risk to provide incentives for him to increase the efficiency of his organization. Many such systems do not include as underwriting factors the medical status of the patient. Failure to include adjustment for the patient's medical status can: 1) leave the provider at risk due to real variation in the mix of the medical needs of the enrolled population (i.e., in areas with a sicker than average patient population, HMOs can fail by simply providing appropriate levels of care) and 2) provide incentives for selective enrollment and disenrollment based on the beneficiaries' medical status to see if such financial loss can be avoided. The authors analyzed two capitation reimbursement scenarios with adjustments for medical status to see if such adverse effects could be avoided while maintaining incentives for efficiency.

Capitation Fee↗
PubMed1989

Case-mix adjusted analyses of service utilization for a Medicaid health insuring organization in Philadelphia.

Health Insuring Organizations (HIOs) are capitated plans that serve all of the Medicaid beneficiaries in a defined catchment area. While this approach to capitation eliminates the incentive to enroll only the healthiest beneficiaries in the area, it does not alleviate concerns that the HIO will respond to the incentives for efficiency created by capitation payment by underproviding services. The authors studied change in service utilization patterns produced by the HIO by using a multivariate strategy to identify case-mix groups at the population level to adjust analyses of hospital and nursing home utilization for case mix. This approach was applied to service utilization data for Medicaid beneficiaries in Philadelphia who received medical services from an HIO and for two control groups. In addition to identifying changes in service use, they evaluated the performance of the HIOs on three dimensions--access to care, quality of care, and the efficiency with which the care was provided. While limitations on the information available in the billing files did not allow definitive statements to be made regarding these issues, case-mix adjusted patterns of service use (and mortality) across sets of service may enable Medicaid programs to identify areas where problems in one of these three critical areas exist. This would allow the program to target its limited utilization and quality review resources toward the areas, types of people, and/or providers where problems in one or more of these areas are more likely.

Actuarial Analysis↗
PubMed1989

Cost effectiveness of home and community-based care.

Medicaid section 2176 waivers allow States to provide home and community-based care to Medicaid eligibles who, but for these services, would enter Medicaid-funded nursing homes. One of the conditions required by Congress for granting these waivers is that this substitution results in no additional Medicaid spending (budget neutrality). The results of case studies of two of these waiver programs, one in California and one in Georgia, are presented in this article. The case studies contain a description of the operation of these programs in some detail. Next, the data and techniques needed to assess the ability of these programs to achieve budget neutrality are presented, and the performance of these programs along this dimension is evaluated.

Activities of Daily Living↗
PubMed1989

Epidemiological, demographic, and social correlates of disability among the elderly.

The magnitude and quality of the problem of disability for the United States elderly population was analyzed in a series of projections. An analysis of the impact of disability on this population is more difficult than for other disabled groups because previously, in both the popular and scientific literature, there was the assumption that the prevalence and severity of disability was a natural consequence of the aging process. Such a perspective has implications not only for initiatives to improve the health and functional states of the elderly population but also for the perception of the level of disability, the handicaps associated with it, and the types of services that are appropriately provided. This image of the natural emergence of frailty with age is now challenged by a number of studies. The extreme heterogeneity of functional status in even the oldest-old (those aged 85 and over) population is evidence that functional impairment among the elderly is not a natural consequence of aging and must be evaluated on an individual basis. There is also increasing evidence that the physiological processes generating impairment are subject to intervention and, in some cases, may even be partly reversed and function regained. Recent research has begun to identify the risk factors for such processes and to explicate the mechanisms of these processes so that more effective interventions can be developed. Whatever interventions may be introduced, the demographic aging of the population will cause large increases in the number of disabled elderly. This is a national problem whose magnitude will depend upon the degree to which the broadly defined needs of this population are or are not met. We considered needs on a number of levels. In terms of basic self-care only bathing and toileting are reported as currently "unmet" to a considerable degree. The most serious deficiencies on a relative basis were for physical equipment and changes in the built environment. All of these factors contribute to a general assessment of changes in the size, structure, and needs of the disabled elderly population. It is clear that no single response will suffice given the magnitude of the problems. Thus, a multidimensional approach involving the private sector and state and federal programs, and their coordination, will be needed to develop adequate responses to the problem.(ABSTRACT TRUNCATED AT 400 WORDS)

Activities of Daily Living↗
PubMed1988

Depressive symptoms and depressive diagnoses in a community population. Use of a new procedure for analysis of psychiatric classification.

A multivariate classification technique was used to examine whether depressive symptoms and symptoms frequently associated with depressive disorders would cluster into recognizable syndromes that parallel traditional DSM-III psychiatric diagnoses. An analysis was made of all respondents in the Epidemiologic Catchment Area (ECA) project of the Piedmont region of North Carolina who reported suffering from depressive symptoms (n = 406) at the second wave of the ECA study. The analysis identified five profiles of symptoms that adequately described the interrelationships of the symptoms as reported in the population. One profile included a set of symptoms nearly identical to the symptoms associated with the DSM-III classification of major depression. Other depressive syndromes emerged and included a premenstrual syndrome among younger women and a mixed anxiety/depression syndrome. The existence of these other depressive syndromes may explain the present discrepancy in the epidemiologic literature between a high prevalence of depressive symptoms and a low prevalence of traditional depressive diagnoses in community populations.

Adolescent↗