Exercise is not only important to help keep our bodies in shape, but when older people are physically active, their brains stay sharper for longer.

A direct link between physical activity and cognitive health had been seen in the brains of laboratory mice, but now, for the first time, researchers have been able to establish a direct connection in humans, too. Using data from the Memory and Aging Project at Rush University of Chicago, researchers tracked the physical activity of over 400 elderly participants who also agreed to donate their brains after they died.

The team was able to look at the seniors' lifestyles and fitness levels and the accumulations of proteins connected with cognitive decline in their brains after death.

Elderly people in the study who remained physically active in their later years had higher levels of healthy proteins in their brains.

The brains of older adults are less likely to function properly if they’ve accumulated amyloid and tau proteins, sometimes likened to the brain’s trash. Eventually these accumulations cause synapses and neurons to weaken and fall apart, contributing to the development of Alzheimer’s disease.

The research suggests a possible way to prevent the accumulation of these waste proteins — exercise. Lead author, Kaitlin Casaletto, an assistant professor of neurology at the University of California, San Francisco and senior author William Honer, a professor of psychiatry at the University of British Columbia, observed that elderly people in the study who remained physically active in their later years had higher levels of healthy proteins in their brains.

The healthy proteins facilitated the exchange of information between neurons, specifically in the brain’s synapses. Casaletto explained the importance of their findings in a press statement: “Maintaining the integrity of these connections between neurons may be vital to fending off dementia, since the synapse is really the site where cognition happens.” She added, “Physical activity — a readily available tool — may help boost this synaptic functioning.”

This conclusion is underscored by Honer’s earlier research indicating that older people who had higher levels of healthy proteins in their brains when they died had experienced better cognitive function later in their lives. “It may be that physical activity exerts a global sustaining effect, supporting and stimulating healthy function of proteins that facilitate synaptic transmission throughout the brain,” Honer explained.

Of course, as we age it’s often necessary to tailor physical activities to accommodate individual limitations. Still, the Centers for Disease Control and Prevention recommends that seniors remain as active as possible. For folks without special needs, at least 150 minutes a week of moderate intensity activity such as brisk walking. Activities that strengthen muscles including weight training are also recommended.

The study is published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.