Associations of cardiorespiratory fitness with cerebral cortical thickness and gray matter volume across the adult lifespan.

High cardiorespiratory fitness (CRF) is associated with reduced cortical thinning and gray matter (GM) shrinkage in older adults. We investigated associations of CRF measured with peak oxygen consumption (V̇o_2peak) with cortical thickness and GM volume across the adult lifespan. We hypothesized that higher CRF is associated with less cortical thinning and GM shrinkage across the adult lifespan, which is associated with better cognitive performance. This cross-sectional study recruited 172 sedentary yet healthy adults (65% women, 22-81 yr) who underwent treadmill exercise testing to measure V̇o_2peak, structural magnetic resonance imaging to assess cortical thickness and GM volume, and a comprehensive cognitive test battery to assess fluid cognitive function. Linear regression models were used to examine the associations of total and regional cortical thickness and GM volume with age, V̇o_2peak, and age × V̇o_2peak interaction after adjusting for sex, education, and total intracranial volume, and the associations of cortical thickness and GM volume with fluid cognitive performance. Mean and regional cortical thickness and total GM volume were associated negatively with age, whereas no associations were observed with V̇o_2peak. However, a significant interaction between age and V̇o_2peak on the right superior parietal volume indicated that aging was associated with smaller right superior parietal volume in the lower CRF group, whereas no association was observed in the higher CRF group. Larger right superior parietal volume was associated with better fluid cognitive performance. These findings highlight the importance of maintaining CRF to prevent or slow brain aging from an adult lifespan perspective.NEW & NOTEWORTHY High cardiorespiratory fitness may mitigate regional gray matter shrinkage across the adult lifespan.