Social vulnerability and prefrontal cortical function in elderly people: a report from the Canadian Study of Health and Aging

Prefrontal cortical lobe function is related to social behavior in humans. We investigated whether performance on tests of prefrontal cortical function was associated with social vulnerability. Associations with non-frontal cognitive function were investigated for comparison.

1216 participants aged 70+ of the Canadian Study of Health and Aging-2 screening examination, who also underwent detailed neuropsychological testing, comprised the study sample. Performance on WAIS-R abstraction, WAIS-R comprehension, Trails B, FAS and category verbal fluency, Block construction, Token Test and Wechsler Memory Scale Information Subset was tested in relation to the participant's level of social vulnerability using regression models adjusted for age, education, sex, frailty, MMSE score, diagnosis of depression, and use of psychoactive medications. Social vulnerability was measured by an index comprising many social problems or "deficits".

The most socially vulnerable group had worse performance on FAS verbal fluency, generating 4.1 fewer words (95% CI: 1.8-6.4, p<0.001) than those in the least socially vulnerable group; those with intermediate social vulnerability generated 2.6 fewer words (95% CI: 0.4-4.8, p = 0.02). Social vulnerability was also associated, though less strongly, with category verbal fluency. The most socially vulnerable people had impaired performance on the Trails B, taking 37 seconds longer (95% CI: 11-63, p = 0.005). These results were independent of age, education, sex, frailty, MMSE score, depression, and psychoactive medications. Social vulnerability was not associated with performance on WAIS-R abstraction, WAIS-R comprehension, Block Design, Token Test or Wechsler Memory Scale tests.

High social vulnerability was associated with impaired performance on verbal fluency and set shifting but not with common sense judgment, abstraction, long-term memory, constructional ability, or language comprehension. The association between social functioning and the cognitive functions subserved by prefrontal cortex warrants further study.