Childhood mental ability and dementia.

OBJECTIVE: To examine links between childhood mental ability and dementia using data from a 1932 survey of the mental ability of the 1921 Scottish birth cohort.
METHOD: Patients with dementia from the 1921 Scottish birth cohort were located in 1) a national survey of early-onset dementia (1974-1988), 2) local mental health services, and 3) a survey of 264 of 519 surviving Aberdeen residents who took the 1932 test. Control subjects were identified in the 1932 Scottish Mental Survey.
RESULTS: Mean 1932 ability score for the Scottish 1921 cohort did not differ from early-onset dementia. Early-onset dementia was not associated with lower childhood mental ability when compared with matched control subjects. In Aberdeen, mental ability scores were significantly lower in children who eventually developed late-onset dementia when compared with other Aberdeen children tested in 1932. This difference was also detected between cases and tested subjects (controls) alive in 1994.
CONCLUSIONS: Late-onset dementia is associated with lower mental ability scores in childhood. Early-onset dementia mental ability scores did not differ from locally matched control subjects or from late-onset dementia. Mechanisms that account for the link between lower mental ability and late-onset dementia are probably not relevant to early-onset dementia.