Scientists know exercise can help protect against dementia and Alzheimer’s disease.
But a new study suggests that physical activity can help prevent the slow decline of cognitive function that comes with aging as well.
In “Leisure-time physical activity associates with cognitive decline: The Northern Manhattan Study,” published in a forthcoming volume of the journal Neurology, researchers at the University of Miami in Florida and Columbia University in New York found moderate to intense physical activity was associated with a slower decline in cognitive function among those who showed no signs of impairment during the first test.
As one part of the ongoing Northern Manhattan Study, which has enrolled thousands of New Yorkers from one community since 1990, researchers tested 1,228 men and women of mixed ethnic and educational backgrounds with a mean age of 71 for their cognitive abilities using memory and problem-solving tests and MRI imaging.
Five years later, they performed the same tests on 876 of the same subjects and asked questions about their level of physical activity. Mental processing speed and episodic memory declined more in subjects who did no exercise or only light exercise, the study showed.
“This study supports the idea physical activity is important to cognition in older adults,” said physician and neurologist Dr. Clinton Wright, co-author of the study, which was funded by the U.S. National Institutes of Health. “Older adults should be aware of that connection.”
The results were more significant among people who had no apparent cognitive impairments at the outset, meaning that interventions like increased exercise — at any age — should be recommended before any symptoms of cognitive impairments are visible and irreversible.
“You start to decline around 25 (years old),” he said. “We’re all suffering cognitive decline, that’s the bottom line.”
But the decline between 75 and 80 is steeper than between 25 and 30, he said. The decline is equivalent to 10 years of cognitive aging, Wright said.
The study grouped those who did no exercise with those who did light exercise, meaning that an evening stroll or light gardening might not be enough to ward off the effects of aging, Wright said. Tennis, running or swimming would be considered moderate to heavy exercise, he said, adding a clinical trial would better determine what intensity of exercise is most effective.
One hypothesis for why physical activity could protect against mental decline is that exercise reduces incidence rates of diseases such as diabetes and protects against organ damage, including that of the brain. It’s also associated with lower rates of silent brain infarction, or silent strokes that patients may not realize they have had, but which are visible on an MRI. It may also be linked to development of nerve tissue and blood vessel development and connectivity of neurons in the brain.