Cohort Effects in Age Associated Cognitive Trajectories

Hiroko H. Dodge, University of Michigan and Oregon Health & Science University
Ching-Wen Lee, University of Pittsburgh
Chung-Chou Ho Chang, University of Pittsburgh
Mary Ganguli, University of Pittsburgh

The age-specific prevalence and incidence of dementia and cognitive impairment in the United States have been either stable or even slightly declining during the 1980s-1990s. One of the suggested but as yet untested reasons of for this improving cognitive function over time is higher educational attainments among more recent cohorts. We used data from two large prospective population-based epidemiological dementia studies, covering the period of 1987 to 2012. Our aims are to examine whether 1) cohort effects exist in age-associated trajectory of cognitive functions, and 2) the observed cohort effects could be explained by educational attainment. We examined age*cohort interactions in mixed effects models with/without controlling for education effects. We observed strong cohort effects with the more recent cohorts showing less age-associated cognitive trajectories. Surprisingly the cohort effects remained very significant after controlling for educational effects. Factors other than education are likely responsible for the cohort effects in cognitive decline.