Lifelong exercise promotes brain health in older adults

Individuals who maintain a regimen of physical activity throughout their lives may prevent brain deterioration during middle and older adulthood. NIA researchers made the discovery by measuring cardiorespiratory fitness in 125 cognitively unimpaired adults, ranging in age from 22 to 94, and by examining their brains. Specifically, they assessed the white matter of the brain, which is composed of myelin, a fatty layer of insulation that surrounds neurons. The study suggests lifelong exercise could be a therapeutic strategy for promoting brain health and reducing the risk of developing neurodegenerative conditions, such as Alzheimer's and Parkinson's disease. The findings were published in Proceedings of the National Academy of Sciences.

Myelin, which tends to decrease as humans grow older, has two major functions: protect neurons from insults and harm such as toxic byproducts generated by the brain, and accelerate the communication between different neurons and regions of the brain. Other studies have shown aerobic exercise may preserve and enhance cerebral myelination throughout the adult lifespan, but how it worked remained unknown.

In this study, the research team tracked cardiovascular fitness levels by measuring maximum oxygen consumption. While running on a treadmill, participants breathed through a mask that was connected to equipment that monitored oxygen and carbon dioxide concentrations. Oxygen consumption was calculated every 30 seconds. The highest value, termed VO2max, was expressed in milliliters per kilogram of body weight per minute (mL/kg/min). This method is considered the most accurate way to measure cardiovascular fitness.

To examine myelin content, the researchers used MRI to scan different regions of participants' brains. They analyzed those images using mathematical and physics modeling to extract information on myelin content, called myelin water fraction. The participants were divided into four age groups: 22 to 39 years, 40 to 59 years, 60 to 79 years, and 80 to 94 years.

The scientists saw a strong correlation between cardiovascular fitness and myelin content, with even small improvements in VO2max leading to large boosts in myelin. Participants 40 and older experienced the greatest myelin increase, suggesting if young adults maintain good cardiovascular health throughout their lives, it will pay off later when they reach midlife and beyond by protecting their brain myelin.

The research suggests cardiovascular fitness may be crucial for the production and maintenance of myelin. The authors emphasize study participants were not professional athletes - just average people who exercised regularly - and that workout length and intensity were varied.

This research was supported by NIA grant ZIAAG000353.

NIA leads NIH's systematic planning, development, and implementation of research milestones to achieve the goal of effectively treating and preventing Alzheimer's and related dementias. This research is related to Milestone 8.B, "Increase investment in clinical trials that robustly test a variety of lifestyle and other non-pharmacological interventions. Employ precision medicine research principles in non-pharmacologic intervention studies by incorporating deep molecular profiling and digital/wearable technologies for tracking responsiveness to the intervention."

Reference: Faulkner ME, et al. Evidence of association between higher cardiorespiratory fitness and higher cerebral myelination in aging. Proceedings of the National Academy of Sciences. 2024. Epub Aug. 19. doi: 10.1073/pnas.2402813121.