Price of adaptation - Allostatic load and its health consequences: MacArthur studies of successful aging

Background: Exponential growth in the population of older adults presents clinicians with special concerns about factors affecting risks for declines in cognitive and physical functioning. Objectives: To examine the hypothesis that risks for such declines and for disease outcomes, such as cardiovascular disease, are related to differences in allostatic load, the cumulative physiologic toll exacted on the body over time by efforts to adapt to life experiences. To present an operational definition of allostatic load, along with preliminary evidence of its predictive validity in relation to salient outcomes of aging. Methods: Data from a longitudinal, community- based study of successful aging were used to develop a measure of allostatic load based on 10 parameters reflecting levels of physiologic activity across a range of important regulatory systems. Allostatic load is the sum of the number of parameters for which the subject was rated in the highest-risk quartile. Results: Higher allostatic load scores were associated with poorer cognitive and physical functioning and predicted larger decrements in cognitive and physical functioning as well as being associated with an increased risk for the incidence of cardiovascular disease, independent of sociodemographic and health status risk factors. Conclusions: Findings are consistent with the conceptualization of allostatic load as an index of wear and tear on the body, with elevations in allostatic load predicting an increased risk for a decline in cognitive and physical functioning as well as cardiovascular disease in a cohort of older men and women. From a clinical perspective, the concept of allostatic load may provide the basis for a more comprehensive assessment of major risks in the aging process.