Impact of health conditions on cognitive change in later life: a cross-study comparative analysis.
Date
2012-03-06
Authors
Sparks, Catharine
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Abstract
Relatively few studies have considered how changes in health are associated with changes in cognition in aging populations. Even fewer have investigated the similarities and differences of the health-cognition link evidenced across independent longitudinal studies of aging that differ in country and birth cohort. The main objective of the current research is to evaluate aging-related cognitive change in the context of physical health conditions and to compare patterns and synthesize results across several longitudinal studies of aging. This cross-study evaluation is based on data from three longitudinal studies of aging: 1) the OCTO-Twin Study, a longitudinal investigation of same-sex twin pairs drawn from the population-based Swedish Twin Registry (N = 702; 67% female; mean age is 83.5), 2) the Health and Retirement Study (HRS), a study of middle-aged and older adults in the U.S. (N = 21,364; 57% female; mean age is 65.8), and 3) the English Longitudinal Study of Aging (ELSA), a study of middle-aged and older adults in the U.K. (N = 11,397; 54% female; mean age is 65.3). Data were analyzed using latent growth curve (LGC) analysis to evaluate 1) the impact of diagnosed health conditions and 2) the additive impact of comorbidity on level and rate of change in distinct cognitive outcomes. Our findings indicate that particular health conditions significantly impact initial status and rate of change in cognition, but do so differently across longitudinal studies of aging. The argument is made that the inclusion of health in our predictive models is essential as we try to parse out the effects of pathological aging vs. normative age-related change in cognition. The results of this study show the importance of replication in longitudinal research and for contrasting patterns of effects across independent studies in order to build a cumulative basis for further understanding of the dynamics among aging, health, and cognition in populations that differ in cohort, culture, and country.
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Keywords
older people, health and hygiene, cognition