Exercise and Cognitive Function in Women

Source: Weuve J, et al. Physical activity, including walking, and cognitive function in women. JAMA 2004;292:1454-1461.

Synopsis: The study involves analysis of the Nurses’ Health Study, which began in 1976 when 121,700 female registered nurses 30-55 years of age returned a questionnaire about their medical history and health-related behaviors. To test the present hypothesis that exercise protected against cognitive decline, participants ages 70 and older were queried about lifestyle factors, particularly exercise, and underwent a standardized telephone interview to assess cognition between 1995-2001. A total of 18,766 women enrolled, and 16,466 underwent a second assessment a mean of 1.8 years later. Women who exercised the most were less likely to smoke and more likely to consume moderate amounts of alcohol. Also, cardiovascular disease, pulmonary disease, and diabetes were less prevalent among women who exercised the most. On the global score of cognition, women in the highest quintile of exercise had 20% lower odds of cognitive impairment at baseline, when compared to women in the lowest quintile (odds ratio = 0.8, confidence interval 0.67-0.95). The association was not restricted to women engaging in strenuous activities. Walking the equivalent of at least 1.5 hours per week at a 21- to 30-minute mile pace also was associated with better cognitive performance. The authors suggest that exercise improves the brain’s vascular health by lowering blood pressure, improving lipoprotein profiles, and promoting endothelial function. Exercise also may help by lowering insulin and by directly promoting neuronal survival. The authors do not provide the body mass index or history of use of menopausal hormone therapy for women by quintile of exercise.

Comment by Sarah L. Berga, MD

In the aftermath of the Women’s Health Initiative, physician and patients have been searching for alternative strategies to health maintenance. Most approaches that might be viewed as alternatives also would complement each other, and may even complement menopausal hormone therapy (MHT). Now that it appears that no one strategy can undo the negative effects of a lifetime of bad habits, it is time to get even more serious about quantifying the extent to which lifestyle variables promote health. Fortunately, most lifestyle factors that promote health also make great fashion sense. Gone are the days when the gaunt figure ruled, and smoking was a fashion aid. Best of all, for most lifestyle factors, moderation appears to be the best course. Thus, it is a relief to read another study showing that moderate physical activity is highly beneficial, in this case for the brain.

So much for common sense. Now we need advice as to how we can get ourselves and our patients to adopt a healthy lifestyle. If the answer is clear that lifestyle matters, then how do we promote adherence? First, it has to be recognized that physicians alone cannot be the only advocacy force. We do have influence, and we need to know how to exercise our influence, as well as our bodies. We can start by following our own advice and set an example. We can urge that our workplaces provide healthy foods. We can walk whenever possible. Studies show that simply reminding patients has an effect!

Perhaps the most important message trickling out of the science of health promotion is that combinations count. It appears that there is synergism between healthy lifestyle variables, such that you get greater impact than predicted when you add good diet, exercise, and intellectual stimulation. There are many examples of this type of synergism in the field of prophylaxis.

Take bone health, for example. Even though about 60-70% of bone mass relates to genetics, there are many behaviors that modulate the other 30%, including sufficient vitamin D exposure, sufficient calcium and mineral intake, overall nutritional status, physical fitness, absence of major illness, lack of glucocorticoid excess, sleep hygiene, social integration, and lack of reproductive compromise. By engaging in all of the recommended behaviors, one minimizes the risk of fracture much more than would be predicted. Unfortunately in the past, at least, there was a tendency to think that taking hormones after menopause meant that one did not need to worry so much about vitamin D intake or getting enough exercise or vice versa. It has been commonplace also to assume that sufficient calcium alone would do the trick. Studies now show that calcium alone is relatively ineffective, but that sufficient calcium intake is a necessary to achieve full protection against osteoporosis and fracture, when other health-promoting behaviors are undertaken.

The same principle is likely to hold true for brain, as well as for bone. To maximally protect against dementia and cognitive decline, one has to do more than crossword puzzles. However, we have yet to perfect the recipe that maximally safeguards our brains as we age. In all likelihood, our recommendation will involve encouraging patients to exercise, get enough rest, eat sensibly, treat hypertension, and stay intellectually engaged. Whether MHT also will be part of the armamentarium remains to be seen. Certain forms of MHT may well augment the neuroprotective effects of a healthy lifestyle, but no study has yet to be designed or undertaken that adequately addresses this hypothesis. Until better data about MHT and neuroprotection exist, we must continue to make sure that patients know that lifestyle, including exercise, helps. Indeed, taking the time to conduct a thorough review of lifestyle factors probably makes as much sense as anything that we do in the office to protect the health of women as they age.

Sarah L. Berga, MD, is James Robert McCord Professor and Chair, Department of Gynecology and Obstetrics, Emory University School of Medicine.