Abstract
BackgroundCognitive capabilities in childhood and in late life are inversely associated with mortality rates. However, it is unclear if adult cognition, at a time still relatively free from comorbidity, is associated with subsequent mortality, and whether this explains the associations of early life factors with adult mortality.MethodsWe used data from the MRC National Survey of Health and Development, a birth cohort study prospectively assessing 5362 participants born in 1946. The present analysis includes participants followed up from age 43 and undergoing cognitive assessment (verbal memory and search speed). Mortality outcomes were notified through linkage with a national register. Cox regression was used to estimate mortality hazards in relation to cognitive performance at age 43, adjusting for early life factors, socioeconomic position and health status.ResultsData were available on 3192 individuals. Univariable analyses indicated that adult verbal memory and search speed, parental factors, childhood cognition and educational attainment were associated with mortality. However, multivariable models showed that the mortality associations with earlier life factors were explained by adult cognitive capability. A standard deviation increase in verbal memory and search speed scores was associated with lower mortality rates [hazard ratio (HR) = 0.86, 95% confidence interval (CI) 0.77-0.97, P = 0.02; HR = 0.88, 95% CI 0.78-1.00, P = 0.05, respectively), after adjustment for adult health.ConclusionsCognitive capability in early midlife was inversely associated with mortality rates over 25 years and accounted for the associations of family background, childhood cognitive ability and educational attainment with mortality. These findings, in a nationally representative cohort with long-term follow-up, suggest that building cognitive reserve may improve later life health and survival chances.
Highlights
Cognitive capabilities underpin health and well-being, and inverse relationships with mortality have been consistently described.[1,2,3,4] Observed associations between cognition and mortality may have multiple explanations, perhaps varying in importance at different stages of growth, stability and decline.[5]
Search speed was more strongly associated with cancer mortality (HR 0.77, 95% confidence interval (CI) 0.65-0.91, P < 0.01, with the same adjustments reported above, and no association with verbal memory itself and cancer mortality). These analyses demonstrated an association between cognitive capability in early midlife and all-cause mortality over 25 years of follow-up, with independent effects observed for both verbal memory and search speed
Mortality associations previously shown in the National Survey of Health and Development (NSHD) with factors earlier in life, namely family background, childhood cognition and educational attainment,[16,19] appeared to act through midlife cognitive capability at age 43
Summary
Cognitive capabilities underpin health and well-being, and inverse relationships with mortality have been consistently described.[1,2,3,4] Observed associations between cognition and mortality may have multiple explanations, perhaps varying in importance at different stages of growth, stability and decline.[5]. In the systematic review, adjusting for SEP in childhood did not affect the HR, though accounting for adult SEP and education attenuated the estimates of effect size These observations are consistent with findings from the Medical Research Council (MRC) National Survey of Health and Development (NSHD) demonstrating that childhood cognition explained some, but not all, of the association between childhood SEP and adult mortality in adulthood up to age 60 years, whereas education and adult SEP strongly attenuated the association.[19]. Conclusions: Cognitive capability in early midlife was inversely associated with mortality rates over 25 years and accounted for the associations of family background, childhood cognitive ability and educational attainment with mortality These findings, in a nationally representative cohort with long-term follow-up, suggest that building cognitive reserve may improve later life health and survival chances
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