A recent article by Swift et al. looked at the effects of aerobic exercise on heart health. Midlife women with high blood pressure were assigned to one of three exercise groups—a program of exercise that met National Institutes of Health (NIH) guidelines, one that was half the amount of exercise recommended by the NIH, or one that was 150% of the NIH recommendations. The study did not examine who actually got heart disease. Instead, the researchers looked at the ability of arteries to function normally, which is a precursor to disease. Specifically, the researchers measured one component of artery health called “flow mediated dilation” (FMD)—the ability of arteries to respond normally to changes in blood flow by dilating (getting larger), which is one indicator of “endothelial (the inner lining of the artery) function.” The authors found that aerobic exercise improved flow mediated dilation. The amount of exercise was not important—the authors suggest that once some minimum amount of exercise exists, improvements will occur. They also found that women with problems benefited from exercise, but not those with normal FMD.
Well, I have to admit this isn’t an area of my expertise. I’m not going to evaluate how solid the methodology was, how close to normal the improvements brought the women, compare these results with the entire body of knowledge, all of which are important to really understanding the import of a study. However, I’d like to share some musings that the article triggered.
First, the article assumes that menopause and the menopausal transition increase a woman’s chances of getting heart disease by modifying her precursors and risk factors. The title of the article is: “The Effect of Different Doses of Aerobic Exercise Training on Endothelial Function in Postmenopausal Women With Elevated Blood Pressure”. The introduction states that their research is important because menopause is associated with worsening of heart disease risk factors. However, they are not studying postmenopausal women. They are studying overweight, sedentary women with high blood pressure who are old enough to be postmenopausal. It used to be more commonly stated, as though it is a fact, that menopause increases a woman’s chances of getting actual heart disease. However, this assertion does not appear to be supported by the facts. A recent paper in the British Medical Journal concluded that aging rather than menopause was key: “Heart disease mortality in women increased exponentially throughout all ages, with no special step increase at menopausal ages”. In 2011, the American Heart Association issued the Effectiveness-based Guidelines for the Prevention of Cardiovascular Disease in Women—2011 Update. These guidelines include a long list of risk factors and suggestions for how to prevent disease, such as modifying lifestyle factors like cholesterol and inactivity. Menopause is not included as a risk factor and is mentioned in just one sentence in the document. The line of research that has now arisen which states with equal certainty that risk factors and precursors to heart disease increase with the menopausal transition thus must be looked at critically. Do these changes in precursors really co-vary with menopause? Do they lead to actual disease? How important are they relative to other factors leading to heart disease, like aging or lifestyle?
The article does not, however, suggest that these menopause-related precursors and risk factors doom women to increased heart disease risk. Indeed, the point of the article is that they can be modified through lifestyle changes, here, aerobic exercise. A lifestyle change that can increase health seems like a good thing. However, what also did strike me was something about the meaning of a healthy lifestyle. Sometimes healthy lifestyle is presented as though it is something that is “added on” to normal daily life. Sometimes it’s almost analogous to a medical prescription—take 20 minutes of exercise daily. However, in the article the women who benefited, in terms of improved endothelial function, were the women who had abnormal function. The authors found that a small amount of exercise did the trick, with no additional benefit from increased exercise. So is it that supplementary exercise cured the problem, or was the problem an abnormal lifestyle deficient in exercise? As an analogy, if I don’t have enough vitamin C I might get a disease called scurvy, because my body needs vitamin C. Once I meet my body’s need, I won’t get the disease, I don’t need twice the requirement. The 2008 federal guidelines recommend that adults up to age 65 will get substantial health benefits from two and a half hours a week of moderate aerobic physical activity. Examples of moderate activity are gardening, walking briskly, ballroom dancing, shoveling snow, and stair walking. Maybe the idea is that our bodies need to move, and if we deny them a minimum amount of movement we have an unhealthy lifestyle. Maybe physical movement and activity are bodily needs, along with other components of a healthy diet and lifestyle.
