Most of us focus on physical gains when we go to the gym, from our arms to our legs, but one of the greatest benefits of exercise occurs on the inside — in the brain. High physical fitness levels not only make our body healthy and flexible, but also our brain, especially in old age. A recent study published in the journal Neurology found doing moderate to high- intensity exercise may help protect the mind from age-related cognitive decline, including Alzheimer’s disease.

In modern societies, most people live past middle age, and deaths occur at older ages. The survival rate for females is 81.2 years, while it's 76.4 years for males. However, an increase in longevity means more age-related health problems.

"The number of people over the age of 65 in the United States is on the rise, meaning the public health burden of thinking and memory problems will likely grow," said Dr. Clinton B. Wright, study author from the University of Miami in Miami, Fla., and member of the American Academy of Neurology, in a statement.

Wright and his colleagues analyzed data from over 800 people enrolled in the Northern Manhattan Study to observe the effects of physical activity on mental agility. The participants, with an average age of 70, were asked how often they exercised during the two weeks prior to the study date. Seven years later, each participant was given a standard neuropsychological exam (NPE), and a repeat exam five years later. The NPE tested memory and thinking skills, and was followed by a brain MRI.

The findings revealed 90 percent of the participants reported light exercise (walking, yoga) or no exercise at all. Meanwhile, the remaining 10 percent reported moderate to high-intensity exercise, including running, aerobics, or calisthenics. They were placed in the high activity group.

Out of those who showed no signs of memory and thinking problems at the start of the study, the low activity group experienced a greater decline over five years on tests of how fast they could perform simple tasks and how many words they could remember from a list. The degree of decline was associated with approximately 10 years of brain aging.

Typically, as we age, our brain cells lose the synapse (tree-branch like) connections between them. These connections are necessary for thought. Over time, our brains lose volume, or gray matter, which can make us susceptible to various types of mental decline.

However, as shown in the study, exercise has the ability to forestall brain aging. It yields large cognitive gains, like greater volume of gray matter in the hippocampal region, which is important for memory. In a 2013 study, researchers studied midlife fitness levels and the subsequent development of all-cause dementia in old age. They found those showing the highest fitness levels demonstrated a much lower likelihood of developing dementia than the group with lower levels, a difference that averaged 36 percent.

“Why the brain responds so favorably to exercise is uncertain,” Dr. Morton Tavel, a clinical professor at Indiana University School of Medicine not involved in the study, told Medical Daily. However, he points out previous studies using brain imaging show that brain shrinkage could be delayed by regular exercise, “a finding that raises intriguing possibilities.”

Exercise is an attractive option to reduce the possibility of cognitive impairment because it is low cost and doesn’t interfere with medications. Tavel believes it is also highly likely exercise is more effective than any drugs or supplements in preventing cognitive decline. “Even minor daily activities, such as brisk walking or the equivalent, can likely be beneficial,” he said.

Regular exercise three to five times a week for 30 to 60 minutes can help us stay sharp. Exercise increases blood flow to the brain, helping it stay healthy and working well. It could possibly even help new brain cells grow.

So, perhaps we should work out for better brain health, because “one is never too fit not only for body, but also for mind,” said Tavel.

Source: Willey JZ, Gardener H, Caunca MR et al. Leisure-time physical activity associates with cognitive decline. Neurology. 2016.