Minute effects of sex on the aging brain: A multisample magnetic resonance imaging study of healthy aging and Alzheimer's disease

Age is associated with substantial macrostructural brain changes. While some recent magnetic resonance imaging studies have reported larger age effects in men than women, others find no sex differences. As brain morphometry is a potentially important tool in diagnosis and monitoring of age-related neurological diseases, e.g., Alzheimer's disease (AD), it is important to know whether sex influences brain aging. We analyzed cross-sectional magnetic resonance scans from 1143 healthy participants from seven subsamples provided by four independent research groups. In addition, 96 patients with mild AD were included. Estimates of cortical thickness continuously across the brain surface, as well as volume of 17 subcortical structures, were obtained by use of automated segmentation tools (FreeSurfer). In the healthy participants, no differences in aging slopes between women and men were found in any part of the cortex. Pallidum corrected for intracranial volume showed slightly higher age correlations for men. The analyses were repeated in each of the seven subsamples, and the lack of age x sex interactions was largely replicated. Analyses of the AD sample showed no interactions between sex and age for any brain region. We conclude that sex has negligible effects on the age slope of brain volumes both in healthy participants and in AD.