Relation between cognitive function and mortality in middle-aged adults - The Atherosclerosis Risk in Communities Study

An independent, inverse association between cognitive function and all-cause mortality has been reported in elderly cohorts. The purpose of this study was to determine whether the same association exists in middle-aged persons. The Atherosclerosis Risk in Communities Study is a cohort study initiated in 1987 to investigate the development of atherosclerosis in middle aged persons. Three cognitive function measures were included in the second cohort examination conducted from 1990 to 1992, when the participants were aged 48-67 years: the Delayed Word Recall Test (DWRT), the Digit Symbol Substitution Test (DSST) (a subtest from the Wechsler Adult Intelligence Scale-Revised), and the Word Fluency Test from the Multilingual Aphasia Examination. Cox proportional hazards modeling was used to determine whether all-cause mortality ascertained through 1997 was associated with each measure after adjustment for sociodemographic, biologic, psychologic, and behavioral risk factors. Without adjustment, there was a significantly lower mortality hazard-associated with higher scores on all three measures. After covariate adjustment, the hazard ratios for the DWRT and the DSST remained significant (hazard ratio(1-point DWRT score increment) = 90, 95% confidence interval: 0.84, 0.97; hazard ratio(7-point DSST score increment) = 0.86, 95% confidence interval: 0.80, 0.93). Cognitive function measured in middle age appears to have prognostic importance for life expectancy similar to that reported in elderly adults.