Sex matters: the effect of physical activity on brain perfusion.

Cerebral blood flow (CBF) declines consistently in aging and this decline is a critical component of several late life diseases. Understanding why this occurs in normal aging, prior to pathological changes, is crucial. Physical activity (PA) is a powerful preventative tool to improve vascular health and preserves CBF in both sexes, though females may benefit most throughout the lifespan. There is currently limited knowledge however about what intensity is needed to derive benefit, and if there are sex differences in this relationship with intensity. Here, CBF and PA were investigated according to sex and age. A total of 573 participants aged 36 to 90 years were included from the Human Connectome Lifespan Aging. Linear and quadratic regressions were utilized to investigate relationships among CBF and PA intensities in each of the four groups. Vigorous PA in middle aged males was related to greater CBF (p < 0.05). Older females showed benefit at all intensities (p < 0.05). Middle aged females were least sensitive to the effects of PA. In all groups except older males, hippocampal CBF was only dependent on vigorous PA (p < 0.05). These results highlight the sex-specific relationship between CBF and PA, and the importance of tailoring recommendations to sex and lifespan stage including addressing and updating current public health guidelines to maximize adoption and benefit, specific to brain health.