Physically active older adults may steer clear of Alzheimer’s disease

Earlier studies have suggested that exercise is good for the brain. A recent study published in  Neurology, the medical journal of the American Academy of Neurology, looks at the mechanisms involved in this relationship. The authors posit that exercise helps maintain insulin and body mass index (BMI) levels, and help protect brain volume and thus may forestall dementia.

“These results may help us to understand how physical activity affects brain health, which may guide us in developing strategies to prevent or delay age-related decline in memory and thinking skills,” says study author Geraldine Poisnel, PhD, of Inserm Research Center in Caen, France. “Older adults who are physically active gain cardiovascular benefits, which may result in greater structural brain integrity.”

On the other hand, researchers discovered that the relationship between exercise and the metabolism of glucose in the brain was not influenced by insulin or BMI levels. In people with dementia, the brain shows reduced glucose metabolism.

The researchers enlisted 134 people, average age 69, who did not have any memory problems. The participants filled out surveys about their physical activity over the past year. Then the researchers scanned the brains of the participants, measuring volume and glucose metabolism. They also measured BMI, insulin levels, cholesterol, blood pressure and other data.

The researchers found that the people who participated in the most physical activity had a higher total volume of grey matter in their brains than people with the least amount of physical activity, i.e. an average of about 550,000 cubic millimetres (mm3) compared to about 540,000 mm3.

The scientists also arrived at the same results when they observed the areas of the brain affected by Alzheimer’s disease.

The participants with the most physical activity also had a higher average glucose metabolism rate in the brain than participants with the least amount of activity.

The researchers did not find an association between higher physical activity with how much amyloid plaque people had in their brains. “In the Alzheimer’s brain, abnormal levels of this naturally occurring protein [beta-amyloid protein] clump together to form plaques that collect between neurons and disrupt cell function.”

According to Poisnel, more research is necessary to figure out the mechanisms behind these relationships. “Maintaining a lower BMI through physical activity could help prevent disturbed insulin metabolism that is often seen in ageing, thus promoting brain health,” Poisnel says.

A significant takeaway is that the study does not prove that exercise protects brain volume – what it does is that it shows an association.

The researchers note that a limitation of the study is the fact that exercise was not measured in a scientific setting but was self-reported by the participants.