Abstract
AbstractBackgroundHigh cognitive reserve (CR) has been related to a decreased dementia risk, but the association between CR and survival with independence is unknown. We examined whether lifelong CR accumulation is associated with disability‐free survival and explored the extent to which cognitive function mediates this association.MethodWithin the Rush Memory and Aging Project, 1,633 dementia‐ and disability‐free participants (mean age: 79.3 years) were followed annually for up to 22 years to detect disability and deaths. A lifelong CR indicator was derived based on information about education, early‐life, mid‐life, and late‐life cognitive activities, and late‐life social activity, and categorized into tertiles (low, moderate, and high). Disability was assessed annually in terms of participants’ ability to conduct activities of daily living and survival status was observed during the follow‐up period. Global cognitive function was assessed annually with a battery of 19 tests. Data were analyzed using Cox models, Laplace regression, and generalized structural equation models.ResultDuring the follow‐up (median: 4.35 years, interquartile range: 2.01 to 7.98 years), 1,079 (64.6%) participants died or developed disability. In multi‐adjusted Cox models, CR score was does‐dependently associated with disability/death (hazard ratio [HR] 0.96, confidence interval [CI] 0.93–0.99). Compared to low CR, the multi‐adjusted HR (95% CI) of high CR was 0.82 (0.70–0.95) for disability/death. In Laplace regression, the median disability‐free survival time was prolonged by 0.17 (95% CI 0.05–0.30) years per unit higher CR score, and 0.99 (95% CI 0.28–1.71) years for participants with high CR compared to low CR. In mediation analysis, cognitive function mediated 35.7% of the association between CR and disability‐free survival.ConclusionHigh lifelong CR is associated with prolonged disability‐free survival, and cognitive function mediates about one‐third of this association.
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