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Biomedical subjects

K G Manton

Publications and source records attributed to K G Manton.

At least 19 recordsLinked to original sources
PubMed1992

Risk factor dynamics, mortality and life expectancy differences between eastern and western Finland: the Finnish Cohorts of the Seven Countries Study.

Prior studies have not accounted for male mortality being higher in east than west Finland. Efforts to identify the mechanisms producing higher mortality in the east, due primarily to cardiovascular diseases (CVD), initially focused on a search for new risk factors. An alternate approach is to examine the assumptions of the analysis. This was investigated using a model which described (a) changes in risk factors over time, (b) dependency of risk factor effects on age, and (c) interactions and nonlinear effects of risk factors on mortality. The model was applied to 25-year follow-up data from cohorts of eastern (N = 823) and western (N = 888) Finnish men using pulse pressure, diastolic blood pressure, body mass index, total cholesterol, vital capacity index, cigarette smoking, and heart rate as risk factors. At age 40, men in the west had a life expectancy 2.4 years higher. Of the difference 29% (0.7 years) was associated with area differences in risk factor means, variances, and their change with age. The remainder, 1.7 years, was associated with age differences in the relation of risk factor interactions to CVD mortality. Possible reasons for these differences, such as joint elevation of several risk factors inducing rapid progression of atherogenesis, are discussed. No significant area differences were observed for mortality from either cancer or other causes.

Adult↗
PubMed1992

Forecasting health: data needs and implications for model structure.

An agenda for analysing data on the health and functioning of the elderly must indicate new types of data to be collected, innovations in data collection strategies and new methods for analysis and forecasting. The required research agenda is broad and will require inputs from investigators in a number of disciplines. The data and methods required will need to be developed in order to reflect national, regional and local variations in the health phenomena under study; they will also have to be responsive to these variations. In the end, however, if the investment is to be most useful, it must be integrated into simulation and forecasting models, the mechanics of which are based on individual-level processes and not on the elements of the service system.

Breast Neoplasms↗
PubMed1992

Demographics (1950-1987) of breast cancer in birth cohorts of older women.

The effects of screening on breast cancer mortality, incidence, and prevalence were investigated using a general forecasting and simulation model. First, a biologically motivated model of disease incidence and mortality was fit to the breast cancer mortality experience of 15 U.S. White female birth cohorts followed for a 38-year period. The model assumed that breast cancer was the result of two different diseases. The first, or "premenopausal" disease, tends to have strong associations with the family history of disease and to be histologically more aggressive. The second, "postmenopausal" disease, occurs at more advanced ages, is apparently less strongly linked to family history, and is less aggressive with different histological characteristics (e.g., positive estrogen receptor status). Those results were used to forecast the effects of screening on the stage at diagnosis to simulate a screening program which reduced late-stage diagnoses by 50%. This produced large reductions in breast cancer mortality--an impact larger for disease associated with late age of onset.

Aged↗
PubMed1991

Blood pressure and mortality risk in the elderly.

Blood pressure was assessed between 1981 and 1983 in all persons over age 65 years in three communities (East Boston, Massachusetts; New Haven, Connecticut; and Iowa and Washington countries, Iowa), and cause-specific mortality was monitored annually over the subsequent 5 years as part of the National Institute on Aging-sponsored Established Populations for Epidemiologic Studies of the Elderly. Each community had 80% or more participation: in East Boston, 3,809 persons with 903 deaths, in New Haven, 2,812 persons with 804 deaths, and in Iowa, 3,673 persons with 763 deaths. At 2 years, odds of death from all causes were higher in the low (less than 130 mmHg) than the middle (130-159 mmHg) systolic blood pressure group for persons aged 65-79 years in all three populations. By 5 years, cardiovascular death increased with increasing systolic pressure in all three communities and reached significance in Iowa. Cancer death was highest in the low systolic pressure stratum in all three centers. All-cause, cardiovascular death, and cancer mortality was highest in the low (less than 75 mmHg) diastolic blood pressure group in East Boston, even at 5 years. Blood pressures obtained 9 years earlier in 2,079 (68%) of the East Boston participants showed a significantly higher risk of cardiovascular death with increasing systolic pressure and no relation between diastolic pressure and mortality risk. In the elderly, excess mortality at lower levels of blood pressure during early follow-up may in part be due to the effects of illness and disability present at baseline. This may obscure the usual rise in mortality with increasing systolic pressure. There is no consistent relation between diastolic pressure and mortality.

Aged↗
PubMed1991

Analyses of black and white differentials in the age trajectory of mortality in two closed cohort studies.

We examine the relationship of age to mortality in blacks and whites in two cohort studies, the 20-year follow-up of the Evans County, Georgia. Study population and the 25-year follow-up of the Charleston Heart Study population. We conducted analyses with two parametric forms of hazard models (Gompertz and Weibull) for total mortality experience and considered the fit of the two hazard models in each study both separately and with the data pooled. We evaluated the robustness of conclusions about differences in the age pattern of mortality for blacks and whites by comparing results from the two hazard models. Where the tests were non-nested, we used an information-based statistic (AIC) to compare the fit of the models to the data. Results were robust to the selection of the hazard function, that is both models provided evidence that mortality rates at younger ages were lower for white than black females but that mortality rates increased more rapidly with age for white females. The absolute differences and the differences in the rates of increase were in the same direction, but smaller, for males. Though both models represented the general features of mortality patterns, the information statistic suggested better performance of the Gompertz function. The Gompertz function was also less sensitive to the initial age of determination of mortality exposure.

Adult↗
PubMed1991

Grade of Membership generalizations and aging research.

The Grade of Membership (GOM) model is a general multivariate procedure for analyzing high dimensional discrete response data. It does this by estimating, using maximum likelihood principles, two types of parameters. One describes the probability that a person who is exactly like one of the K analytically defined types has a particular response on a given variable. The second describes each individual's degree of membership in each of the K types. This "partial" membership score reflects the logic of the fuzzy partitions (rather than of discrete groups) that are employed in the analyses. By modifying the probability structure of the basic model we show how the procedure can be applied to a number of different types of data and analytic problems. The utility of the different GOM models for different types of aging research is discussed.

Aging↗
PubMed1991

Cross-sectional estimates of active life expectancy for the U.S. elderly and oldest-old populations.

Estimates are made of active life expectancy for the U.S. elderly and oldest-old populations using data from the 1982 and 1984 National Long Term Care Surveys. In the calculation of active life expectancy a multivariate analysis of 27 measures of functioning was used to define scores to decompose total life expectancy by type and level of disability. These analyses showed significant differences in active life expectancy for males and females. Though a higher proportion of male life expectancy at age 65 was "active," females had larger absolute amounts of active life expectancy. By age 85, in contrast, males had a higher absolute amount of active life expectancy. In addition, calculations were performed with the disability associated with cognitive impairment eliminated in order to illustrate the sensitivity of active life expectancy to changes in morbidity.

Activities of Daily Living↗
PubMed1991

Cancer mortality, aging, and patterns of comorbidity in the United States: 1968 to 1986.

Cancer is often reported as contributing to the risk of noncancer causes of death. The age variation of these reports was studied using U.S. data on all causes of death listed on death certificates for 1968 to 1986. The occurrence of cancer as a nonunderlying cause of death increased with age and was higher for treatable and slowly growing tumor types. These patterns persisted even if the cancer manifested changes in occurrence. Nonunderlying occurrences were highest in the 85 to 94 age group and were correlated with cancer survival. This suggests increased importance of cancer as a cause of death and a comorbid condition among oldest-old persons. The high rate of occurrence as an associated cause of death suggests that if life expectancy increases due to declines in circulatory and other chronic disease mortality, cancer could become the preeminent cause of death in the United States.

Age Factors↗
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

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 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↗