New research suggests that the relationship between physical and brain fitness varies in older adults by virtue of their sex. The study is publishing ahead of print in the Journal of Applied Physiology.
The researchers investigated sex differences in the association between a measure of physical health, cardiorespiratory fitness (CRF), and brain function using resting state functional connectivity fMRI. They examined these sex differences in the default, frontoparietal control, and cingulo-opercular networks, assemblies of functionally connected brain regions known to be impacted by both age and fitness level.
A total of 49 healthy older adults (29 female) were scanned to obtain measures of intrinsic connectivity within and across these three networks. Also, they calculated global efficiency (a measure of network integration), and local efficiency (a measure of network specialization) using graph theoretical methods. Across all three networks combined local efficiency was positively associating with CRF, and this was more robust in male versus female older adults.

Brain network integrity and physical health

Further, global efficiency was negatively associating with CRF, but only in males. Moreover, findings suggest that in older adults, associations between brain network integrity and physical health are sex-dependent. These results underscore the importance of considering sex differences when examining associations between fitness and brain function in older adulthood.

Cardiorespiratory fitness is the measuring oxygen delivering to the muscles. Fitness level has also been associating with changes in the brain’s nerve-rich tissue; called gray matter, and better cognitive function in later life. Previous studies have also found cardiorespiratory fitness to be related to how the brain functions during periods of rest. Nerve connectivity in the brain during rest changes with age.
These changes can negatively affect cognitive function. However, “the neural basis of sex differences in the relationship between fitness and brain function in older adults has not been directly explored,” wrote researchers from York University and McGill University in Canada.

Fitness and brain function in older adults

The research team studied one group of men and one of women, both with an average age of 67. The volunteers self-reported their typical daily physical activity level. The research team recorded the participants’ height, weight, age, sex and resting heart rate to determine their cardiorespiratory fitness. They also administered imaging tests of the brain to record nerve function; both within specific brain networks (local efficiency) and among all networks (global efficiency).
The men having higher cardiorespiratory fitness levels than the women. However, the women had higher local network efficiency and lower global network efficiency than the men. This pattern of connectivity was more robust in the women; and has been positively associating with executive function; which are skills that contribute to being able to focus, pay attention and manage time. Fitness levels, however, were more strongly associating with improving this brain efficiency pattern for men than women.
“Our findings that cardiorespiratory fitness is associating with brain function in a sex-dependent manner underscore; the importance of considering sex as a factor; when studying associations between exercise and brain health in older adulthood,” the researchers wrote.