Age, medical conditions, and gender as interactive predictors of cognitive performance: the effects of selective survival.

The interaction of age, medical conditions, and gender on free-recall and mental status test performance was analyzed in two large survey samples of older adults. Age, gender, and the presence of medical conditions interacted with recall and mental status in Study 1 (n = 2,695) and mental status in Study 2 (n = 6,299). For men, those with one or more medical conditions declined more steeply with age than those with no conditions. For women, this relationship was reversed. The findings suggest survival effects, whereby those who lived to old age with medical conditions and were selected into the sample had high levels of cognitive functioning. The age at which these effects are seen vary with gender because women survive longer than men.