Cognitive function in the oldest old: women perform better than men

It is possible that gender differences in cognitive function in aged persons can be explained by limited formal education, which is more common in women than in men. This study measured cognitive speed and memory in 85-year-old men and women in Leiden, The Netherlands, to confirm whether sex influences cognition and whether differences in formal education are relevant. A total of 599 individuals, 87% of Leiden residents 85 years of age, were visited at their residences and completed the Mini-Mental State Examination (MMSE). Cognitive speed and memory were estimated by neuropsychological tests when the MMSE score exceeded 18 points. Cognitive speed was measured using the abbreviated 40-item Stroop test of attention and the letter-digit coding test of processing speed. Memory function was estimated with the 12-word learning test of immediate and delayed recall. Significantly more women than men had had no schooling or primary school education only (70 vs. 53%). Nevertheless, women had better scores for both cognitive speed and memory than did men. After adjusting for educational differences and depressive symptoms, the odds ratio for women having higher cognitive speed was 1.7, and for better memory, 1.8. Women recalled more words than men on the immediate word learning test but had similar test scores on the delayed word learning measure. Those with more education had significantly higher test scores for cognitive speed. Men and women lacking depressive symptoms scored significantly better on all tests. The effects of educational level and depression on cognitive function were similar in women and men. Despite a lower educational level, women aged 85 years in this study exhibited better overall cognitive function than did men of the same age. Rather than education being the controlling factor, better cognitive function in women is likelier to represent some biological factor, such as atherosclerotic disease.