Implications of Lifecourse Epidemiology for Research on Determinants of Adult Disease

Abstract

Many diseases commonly associated with aging are now thought to have social and physiologic antecedents in early life. Understanding how the timing of exposure to early life risk factors influences later-life health may illuminate mechanisms driving adult health inequalities and identify possible points for effective interventions. Recognizing chronic diseases as developing across the lifecourse also has implications for the conduct of research on adult risk factors for disease. We review alternative conceptual models that describe how the timing of risk factor exposure relates to the development of disease. We propose some expansions of lifecourse models to improve their relevance for research on adult chronic disease, using the relationship between education and adult cognitive decline and dementia as an example. We discuss the important implications each of the lifecourse conceptual models has on study design, analysis, and interpretation of research on aging and chronic diseases. We summarize several research considerations implied by the lifecourse framework, including: advantages of analyzing change in function rather than onset of impairment; the pervasive challenge of survivor bias; the importance of controlling for possible confounding by early life conditions; and the likely heterogeneity in responses of adults to treatment.

Keywords: Lifecourse epidemiology; aging; chronic disease; dementia; models.

Fig. 1

Alternative lifecourse models linking the timing of exposure to stimulating cognitive environment and dementia risk. (a) Immediate risk; (b) Social trajectory; (c) Cumulative risk; (d) Early life latency; (e) Social mobility effects.

Fig. 2

Alternative cognitive trajectories across the lifecourse, resulting in meeting threshold criteria at the same age. (a) Longer period of cognitive development but faster rate of age-related decline. (b) More severe cognitive decrements after stroke, but greater neurologic recovery.

Fig. 3

Lifecourse model distinguishing between developmental, pathological, and recovery processes linking education or cognitive engagement to dementia.

Fig. 4

Individuals who experience advantage across life and arrive at middle age with high cognitive function may experience cognitive decline more slowly than those who encounter disadvantage across life. If so, this will result in greater increasing variability in cognitive function across age.