Walking Compared with Vigorous Exercise for the Prevention of Cardiovascular Events in Women

Abstract & Commentary

Synopsis: Prospective, but nonrandomized, data indicated that both walking and vigorous exercise are associated with substantial reductions in the incidence of cardiovascular events among postmenopausal women, regardless of race, ethnic group, age, or body mass index. Prolonged sitting increased the risk of cardiovascular disease.

Source: Manson JE, et al. N Engl J Med. 2002;347: 716-725.

In this study, Manson and Associates sought to determine the relationship between exercise and cardiovascular health by using the data collected in the Women’s Health Initiative Observational Study (WHI-OS). They calculated a total physical activity score and correlated it with the incidence of coronary events and total cardiovascular events among 73,743 postmenopausal women ages 50-79 years. Vigorous exercise was defined as that in which "you work up a sweat and your heart beats fast" and included aerobics, jogging, tennis, and swimming laps. Participants were also asked to report moderate and mild forms of exercise as well as the hours per day spent engaged in sedentary behavior, including sitting, lying down, and sleeping. The primary end points were newly diagnosed coronary heart disease and total cardiovascular events. Potential confounding variables that were controlled for included age, smoking history, body mass index (BMI), waist/hip circumference, alcohol consumption, age at menopause, use of hormone replacement therapy, parental history of premature cardiovascular disease, race or ethnic group, education, family income, and dietary variables.

During a mean follow-up time of 3.2 years, there were 345 newly diagnosed cases of coronary disease, 309 strokes, and 1551 cardiovascular events. A strong inverse and graded relationship was found between total physical activity score and the risk of coronary heart disease. Risk reduction was similar for walking and vigorous exercise and maximal for those who engaged in both walking and vigorous exercise. These associations were seen regardless of age, race, and BMI. Walking pace was an important determinant of risk reduction. After accounting for age and energy expenditure, the relative risk of cardiovascular disease was increased among women who were sedentary for 16 hours vs. 4 hours daily, with a relative risk of 1.68 (1.07-2.64).

Comment by Sarah L. Berga, MD

Am I killing myself as I sit here writing this commentary? Are you killing yourself while you sit there reading it? Most of us have jobs that involve a lot of reading and writing. Is it possible to counteract all that sitting with bouts of exercise? What should we advise our patients? I lead a relatively active life, but most of the activities that comprise an academic life involve sitting. It is very difficult to read journals and grants while running. I have seen some people try while on the treadmill or stationary exercise bike, but I wonder how much information they absorb while multi-tasking in that manner. I cannot imagine how one could run on the treadmill and type on a computer, although I must acknowledge that I have never tried it and, until I read this article, I had no reason to think that I should try. I suspect that your predicament is not so dissimilar.

Like most good studies, this one raises as many questions as it answers. It seems to imply that you cannot make up for hours of sitting by an hour of running or walking. This is disturbing, because I think that this is the strategy that most busy professionals use in their daily life. If you have a ton of desk work to do, you try to do it efficiently and then look for those opportunities to give the body a break. What if it doesn’t work that way? Then we would have to seriously think about how to redesign our approach to work. Modern society depends on paperwork, even if we do it electronically. Lots of forms are needed to sell and buy and distribute the goods. And if we eat high-fat, high-carbohydrate foods while doing that paperwork, it is even worse for our waistlines and cardiovascular health.

Despite the embedded perversity about sitting, this study does offer lots of answers. The main point is that no matter who you are, walking will improve your cardiovascular health. This is the information patients need to hear. Any amount of exercise will help, so it is important to do some. This study did not find an upper limit to the benefit of ever-increasing amounts of exercise, although we know that too much exercise can compromise reproductive competence, especially when coupled with undernutrition. This is hardly a worry of relevance for the majority of postmenopausal women, however, because most are battling the bulge and years of relative inactivity.

This article was not the lead one for this week of the New England Journal of Medicine. Instead, the editors chose one on the deplorable degree of physical inactivity in adolescent girls.1 The editorial by cardiologist Paul Thompson focused on both articles.2 Essentially, the issue of physical inactivity is relevant for all of us, men and women alike, at all ages. Dr. Thompson notes, however, that in the Harvard Alumni Study,3 no further reduction in cardiovascular events was found in men with an energy expenditure of more than 2000 Kcal per week, a value that corresponds to the highest quintile in the WHI-OS study of postmenopausal women. Thus, he suggests that there is a threshold effect or at least a progressive decline with progressive activity. In short, despite my initial fears, neither you nor I are likely to be killing ourselves by writing or reading this synopsis.

Dr. Berga is Professor and Director Division of Reproductive Endocrinology and Infertility, University of Pittsburgh.

References

1. Kimm SY, et al. N Engl J Med. 2002;347:709-715.

2. Thompson PD. N Engl J Med. 2002;347:755-756.

3. Sesso HD, et al. Circulation. 2000;102:975-980.