We need to do about 75 minutes of vigorous activity a week or 150 minutes of moderate activity.
Higher fitness levels in midlife are associated with a lower risk for dementia in later life, a new study suggests.
"We already know exercise has cardiovascular and many other benefits, but this may give people more incentive to get moving," lead author, Laura F. DeFina, MD, "Dementia is the second most feared disease after cancer, and our research suggests you can lower your risk by keeping fit."
The study is published in the February 5 issue of the Annals of Internal Medicine.
The study included 19,458 individuals participating in the Cooper Clinic Longitudinal Study at the Cooper Institute, a preventive medicine clinic. All underwent standardized fitness testing in midlife (median age, 49.8 years) and were then followed for an average of 25 years.
There were 1659 cases of all-cause dementia reported. After multivariable adjustment, participants with the highest fitness level at midlife had a 36% reduction in risk of developing dementia from any cause during follow-up than those in the lowest fitness category
Dr. DeFina also pointed out that the reduction in dementia was consistent in patients who had had a stroke and in those who hadn't, suggesting that the mechanism does not just involve vascular disease. "Exercise is known to reduce cardiovascular disease, which we would expect to be translated into benefit on stroke, but because we also saw a similar reduction in dementia with improved fitness in patients who hadn't had a stroke, this suggests that other mechanisms are also involved."
She added that animal studies have suggested that increased fitness and activity correlates with a reduction in brain atrophy and loss of cognition, and changes in amyloid have been seen with regular activity.
Although this was a study of fitness, rather than actual physical activity undertaken, Dr. DeFina said the results were consistent with US physical activity guidelines that recommend 150 minutes of moderate exercise or 75 minutes of vigorous activity per week for health benefits.