Good news for walkers! Recent research in
The New England Journal of Medicine
suggests that walking is similar to more vigorous exercise in its ability to reduce the risk of cardiovascular disease in postmenopausal women. The fact that exercise reduces your risk of cardiovascular disease is not news, but the possibility that regular walkers reap heart benefits similar to runners and other vigorous exercisers is. This is particularly good news for women, because research shows that walking is the preferred exercise of many women.
Researchers from several US universities and medical centers collaborated on this study of 73,743 women participating in the Women’s Health Initiative (WHI) Observational Study. The WHI study was composed of 93,676 postmenopausal women who were between the ages of 50 and 79 when they entered the study between 1994 and 1998. Women were excluded from the WHI if they had congestive heart failure, obstructive lung disease, severe liver or kidney disease, alcoholism, mental illness, or dementia. This recent analysis of the WHI data included only WHI participants who could walk and were free of coronary heart disease, stroke, and cancer when they entered the study.
Upon entering the WHI study, participants completed questionnaires about personal and family medical history, physical activity, smoking, diet, and other lifestyle factors. In addition, the following measurements were taken: blood pressure, height, weight, and waist and hip circumferences.
The physical activity questionnaire asked how much time women spent doing the following activities:
walks outside the home of 10 minutes or more without stopping
physical activity that “works up a sweat and makes your heart beat faster” (Examples: aerobics, aerobic dancing, jogging, tennis, swimming laps)
physical activity that is “not exhausting” (Examples: biking outdoors, using an exercise bike or treadmill, calisthenics, easy swimming, dancing)
other physical activity (Examples: slow dancing, bowling, golf)
time spent sitting, lying down, or sleeping
Annual questionnaires were mailed to participants to gather information on “cardiovascular events”—new cardiovascular diagnoses (such as heart disease, heart attack, stroke, congestive heart failure, angina, or death from cardiovascular causes) and revascularization procedures. All diagnoses and procedures were verified by reviewing medical records, laboratory reports, and death certificates.
After an average of three years of follow-up, researchers compared the number of cardiovascular events among women with varying levels of physical activity and sedentary behavior.
Overall, as duration of exercise increased, risk of cardiovascular events decreased. Specifically, women who either walked or exercised vigorously for at least 2.5 hours per week were about 30% less likely to have cardiovascular events than women who did not exercise. In addition, walking at faster paces provided more benefit than walking at slower paces.
On the flip side, time spent sitting, lying down, or sleeping (sedentary behavior) increased risk of cardiovascular events. Compared with less than 4 hours per day of sedentary behavior, 12 to 15 hours increased risk by nearly 40%; and 16 or more hours increased risk by nearly 70%.
These estimates have been adjusted to reflect the effects of other coronary risk factors, such as age, race, ethnicity, smoking, body mass index (BMI), waist-to-hip ratio, and several dietary factors.
Although these results are compelling, particularly because of the study’s large size, they have their limitations. First, there were no men in this study, and theoretically, men might respond differently to various levels of exercise than women do. However, in previous studies of exercise and cardiovascular disease, results for women and men have generally been similar. Second, self-reported estimates of physical activity can be imprecise. Respondents tend to overestimate the amount of exercise they participate in, which may lead to misclassification of people into higher exercise categories. Third, even though the researchers tried to control for factors other than exercise that may explain the observed benefits, they could not account for all possible confounding factors. People who choose more vigorous lifestyles, for example, may be physiologically, emotionally, or genetically different than less active people. And, it’s possible that other lifestyle factors not accounted for in this study had an effect on cardiovascular disease.
The big news here is that regular walking appears to confer significant cardiovascular benefit. However, this shouldn’t discourage you from doing vigorous activity. Although research on the duration and intensity of exercise necessary for cardiovascular health has not been consistent, more vigorous activity can reasonably be expected to produce even greater health benefits (as long as you avoid getting injured).
If you’re comfortable doing more vigorous exercise, keep up the good work. But for those who prefer walking, there is now a very large study in an ethnically diverse female population that supports your exercise choice. And if you can, consider picking up your pace to 3 to 4 miles per hour—the speed reported by faster walkers in this study.
Although not all authorities agree, the Centers for Disease Control and Prevention and the American College of Sport Medicine recommend “at least 30 minutes of moderately intense physical activity on most, and preferably all, days of the week.” Brisk walking qualifies as “moderately intense.”