Better Midlife Fitness Linked to Lower Dementia Risk
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, from The Cooper Institute, Dallas, Texas, commented to Medscape Medical News. "Dementia is the second most feared disease after cancer, and our research suggests you can lower your risk by keeping fit."
She noted that although there is a lot of literature on physical activity and dementia, a 2010 statement from the National Institutes of Health suggested that evidence was insufficient to promote lifestyle change for brain health because the studies conducted so far have been small, with short follow-up, and the definition of patients and of dementia has been inadequate.
"Our study overcomes many of these shortcomings, with a large homogeneous patient population, an objective measure of fitness, and a long follow-up. We therefore believe our data give a strong message to improve fitness, which we think may be more powerful than some previous attempts at changing behavior."
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. Cases of dementia were found from Medicare claims data.
There were 1659 cases of all-cause dementia reported. After multivariable adjustment, participants with the highest fitness level (quintile 5) at midlife had a 36% reduction in risk of developing dementia from any cause during follow-up than those in the lowest fitness category (quintile 1).
Table. Risk for Dementia With Increasing Fitness Level
| Fitness Quintile | Hazard Ratio for Dementia (95% Confidence Interval) | P Value |
| 1 (lowest fitness level) | 1.00 (reference) | - |
| 2 | 0.88 (0.76 - 1.02) | .089 |
| 3 | 0.79 (0.67 - 0.92) | .002 |
| 4 | 0.70 (0.60 - 0.83) | < .001 |
| 5 (highest fitness level) | 0.64 (0.54 - 0.77) | < .001 |
"The long follow-up time in our study is essential as there is evidence that changes on the brain may begin up to 20 years before dementia starts to become evident," Dr. DeFina noted.
"Another strength of our study is that we objectively measured cardiorespiratory fitness in a uniform way (on a treadmill) in all participants," she added. "Normally studies looking at physical activity rely on self-reported exercise which is notoriously inaccurate."
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.
Never Too Late to Start
The researchers believe that although it is best to achieve fitness earlier in life and keep it up throughout life, benefits could still be seen in people starting later. Dr. DeFina noted: "It is never too late to improve fitness. If you're not 49, there are still functional benefits of being active in your later years."
Coauthor Benjamin L. Willis, MD, MPH, also from the Cooper Institute, added, "The best time to plant a tree is 20 years ago, but the second best time is today."
In an accompanying editorial, Mary Sano, PhD, Mount Sinai School of Medicine, New York, and James J. Peters, Veterans Affairs Medical Center, New York, point out that adherence to exercise regimens is notoriously difficult, and less than 10% of the US population is estimated to achieve the 150-minutes-per-week guideline.
However, they agree that the fear of Alzheimer's disease "may provide both the context for physicians to introduce the topic of physical activity and the motivation for patients to heed advice to increase physical activity."
The study was supported by the Cooper Institute; the University of Texas Southwestern Medical Center; the National Heart, Lung, and Blood Institute; and the American Heart Association. Disclosures are available online with the article.
Ann Intern Med. 2013;158:162-168, 312-214. Abstract Editorial
Medscape Medical News © 2013
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