Relationships between self-reported physical and mental health and intelligence performance across adulthood

One hundred and twenty-seven adults between 20 and 90 years of age were tested on the Wechsler Adult Intelligence Scale for their digit span memory (forward and backward), fluid intelligence (block design and digit symbol), and crystallized intelligence (vocabulary and information), as well as assessed for self-reported health (Cornell Medical Index, Zung Depression Scale, health habits, and self-ratings of physical and mental health). As expected, across the entire age range there was no correlation between age and digit span memory (r = .03), a strong negative correlation between age and fluid intelligence (r = -.78), and a modest positive correlation between age and crystallized intelligence (r = .27). In addition, older adults reported more physical (r = .36) and mental (r = .32) health problems than did younger adults. Of special interest was the finding that both self-reported physical and mental health accounted for significant variance in intelligence performance, particularly in older adults. Moreover, self-reported health accounted for a considerable portion of observed variance, even when age differences in self-reported health were statistically controlled.