O2‐05‐03: Birth Cohort Effects in Memory Function and Practice Effects From Epidemiological Studies of Cognitive Impairment and Dementia
Year: 2016
Type: article
Abstract: Growing evidence suggests the age-specific prevalence and incidence of dementia and cognitive impairment may be stable or even declining over time in the US and other developed countries. Trends in cognitive test performance across birth cohorts may shed light on these effects. Higher educational attainment among the more recently born cohorts is often cited as one of the potential reasons of this trend. Whether age-associated trajectories of memory functions differ by birth cohorts and whether differences can be explained by increasing educational attainment remain unclear. Pooling data from two prospective population-based studies in two contiguous areas in Pennsylvania between 1987 and 2015, we identified four birth cohorts born 1902-1911, 1912-1921, 1922-1931, and 1932-1943. We first harmonized cognitive test scores across the studies since different memory tests (the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) and the Wechsler Memory Scale–Revised (WMS-R)) were administered. Next we compared age-associated trajectories of memory function and the magnitude of practice effects among the birth cohorts. Using mixed effects models, we first included cohorts, cohort x time (i.e., age) interaction terms, practice effects and cohort X practice interaction terms, and then added education effects to examine whether education explained the cohort difference in memory trajectories and practice effects. We observed significant cohort effects in learning (immediate recall scores) with its age-associated trajectories showing less steep declines among the later born cohorts in comparison with the earlier born cohorts, independent of education. We also observed cohort effects in practice effects with the higher levels in the later born cohorts, both in learning and memory (delayed recall scores). We found that the more recently born cohorts are experiencing both lesser declines in age associated trajectories in learning, and also larger practice effects in learning and memory. These differences remained after factoring in educational attainment. The finding is consistent with our earlier finding for other cognitive domains where we showed improved age-associated trajectories among recently born cohorts, independent of education. Secular trends other than education could play roles in recently found trends in improved cognitive health in developed countries.
Source: Alzheimer s & Dementia
Language: English
Subfield: Psychiatry and Mental health
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2536408547