The role of cognitively stimulating activities throughout the lifespan on risk and timing of conversion to dementia

Abstract

AbstractBackgroundPrevious research suggests that modifiable lifestyle factors, such as engagement in cognitively stimulating activities, contributes to cognitive reserve such that some individuals can tolerate more pathological burden before cognitive symptoms emerge. However, it is unclear whether such benefits persist throughout the lifespan or are limited to certain critical periods. The present study sought to explore if cognitive engagement at various points in the lifespan uniquely contributes to cognitive reserve in late life.MethodData were from 1977 older adults from the Memory and Aging Project without dementia at study onset (M age = 80.10 at baseline). Cognitive assessments were performed annually for an average of 7.42 years until death. Each participant agreed to brain donation for post‐mortem analysis of neuropathologies. Multistate survival modeling was used to examine the influence of lifelong cognitive engagement on risk of transitioning between normal cognition, mild cognitive impairment (MCI), dementia, and death states. Life expectancies for individuals with and without cognitive impairment were then estimated. An additional model was run for participants with available neuropathology data (n = 841), accounting for overall pathological burden.ResultsA total of 560 participants developed dementia during the follow‐up period. Cognitive activity in childhood, young and middle adulthood were included as predictors of risk of transitioning between cognitive states, controlling for age, sex, and education. Only midlife cognitive activity predicted cognitive transitions, with higher activity predicting decreased risk of developing MCI (OR = .82, 95% CI: .71, .95). In the subset of participants with pathology data, cognitive activity in midlife predicted decreased risk of transitioning to MCI (OR = .74, 95% CI: .61, .90) after accounting for pathologic burden. Midlife cognitive activity moderated the effect of pathological burden such that individuals high in pathology and high in cognitive activity were more likely to transition directly from healthy cognition to death without developing impairment.ConclusionWith no known cure for Alzheimer’s Disease, delaying the onset of cognitive decline represents a key target for future dementia research. These findings suggest that cognitive engagement in midlife may help to delay impairment and buffer the effect of brain pathologies on cognition.