The researchers defined brisk walking as a form of moderate level of exercise. (iStock)

Keeping the heart pumping through physical activity helps to protect and even reverse memory problems in older adults, two recent studies suggest.

Mild cognitive impairment is often considered a transition stage between normal aging and dementia. People with mild cognitive impairment have memory problems but there is no major disability. Each year, 10 to 15 per cent of people with mild cognitive impairment will develop dementia, researchers say.

In one study published in the January issue of the Archives of Neurology, researchers at the Mayo Clinic in Rochester, Minn., looked at 1,324 people aged 50 to 65 without dementia when the study began. Participants in the aging study completed physical exercise surveys between 2006 and 2008.

Of those studied by the Mayo Clinic team, an expert panel classified 198 as having mild cognitive impairment and the rest had normal cognition.

Those between age 50 and 65 who reported engaging in moderate physical activity, such as playing golf without a cart, swimming or brisk walking, showed a 39 per cent reduction in the odds of developing mild cognitive impairment, the team found.

Similar exercise in later life was associated with a 32 per cent reduction in risk.

Exercise to keep mind sharp

A second study appearing in the same issue found moderate physical activity can treat mild cognitive impairment.

The researchers at the University of Washington looked at 33 patients with an average age of 70 at a memory disorders clinic who were experiencing decline.

The first group of 23 participants was randomly assigned to an aerobic exercise program that involved exercising at high intensity for 45 to 60 minutes each day. The other 10 participated in stretching exercises while keeping their heart rates low.

Fitness testing, body fat analysis, blood tests and assessments of cognitive function such as memory and decision making showed those in the high-intensity exercise program experienced improved cognitive function compared with those in the stretching group.

"Six months of a behavioural intervention involving regular intervals of increased heart rate was sufficient to improve cognitive performance for an at-risk group without the cost and adverse effects associated with most pharmaceutical therapies," Laura Baker of the University of Washington School of Medicine and her colleagues concluded.

The effects of reversing the mind-robbing decline were bigger in women than in men, even though both sexes experienced similar increases in fitness. The difference may result because women's bodies produce and use insulin, glucose and the stress hormone cortisol differently than men, the researchers speculated.

The study's authors also listed several possible reasons why exercise may protect against mild cognitive impairment, including:

• Greater blood flow to the brain.
• Production of nerve-protecting compounds.
• Improved development and survival of neurons.
• Decreased risk of heart and blood vessel disease.

It's also possible that those who engage in physical exercise also tend to eat healthier and adhere to their medications better, the team noted in calling for more research to better understand the cause and effect relationship.