Sex differences in cognitive trajectories and practice effects in a cohort of older Londoners: The role of risk factors

TL;DR

This study finds that women generally perform better on cognitive tests than men, with differences influenced by age and genetic risk factors for Alzheimer's.

Contribution

The study reveals how sex differences in cognitive performance and practice effects vary with age and Apolipoprotein-ε4 status.

Findings

Women outperformed men on most cognitive tests at baseline, with a significant adjusted mean score difference.

Men showed less improvement over time in cognitive domains compared to women.

Older participants and Apolipoprotein-ε4 carriers showed greater sex differences in practice effects.

Abstract

Sex differences in cognitive abilities have been reported; however, the underlying reasons remain unclear.

To (i) investigate sex differences in cognitive performance, (ii) evaluate the contributions of established dementia risk factors to these differences, and (iii) examine the role of non-modifiable risk factors on sex differences in cognitive performance.

Among 964 cognitively unimpaired participants (aged 60–85) of the UK CHARIOT-PRO Main Study, we assessed cross-sectional and longitudinal associations, over up to 3 years of follow-up, between sex and cognitive performance, using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS).

Sex differences, mostly favoring women were observed at baseline across almost all RBANS indices including the total scale (Cohen's d = 0.3, adjusted mean difference in score = −5.4, p < 0.001). Sex differences were observed in Practice effects (PEs), with men showing less PE in almost all cognitive domains including the total scale (adjusted 1.3, p = 0.002). Greater sex differences in PEs, were documented among the ‘older’ participants in two out of five cognitive domains including the immediate memory index (mean difference: older (69–85 years) group = −3.2, p = 0.002); younger (60–68 years) group = −0.8, p = 0.4). Sex differences were more pronounced among ‘Apolipoprotein-Ꜫ4 -carriers’ in three out of five domains including the total scale (mean difference in carriers = −2.6, p = 0.002); non-carriers = −0.7, p = 0.3).

Sex differences in cognition and PE were observed after adjusting for risk factors associated with Alzheimer's disease. Future studies should also consider the effects of sex on non-modifiable risk factors and PEs to identify potential ‘masked’ neuropathology.

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