Women should walk - evidence for exercise benefits

reposted from: Bandolier - full article posted below, unedited. "The bottom line is that women who walk briskly or exercise vigorously for three hours a week or more can reduce their risk of heart disease."

Women should walk

Study Outcomes Results Comment

Bandolier is keen on evidence on healthy living. One of the excellent sources of evidence is the US nurses' health study, started in 1976, when about 122,000 female nurses in the 30 to 55 age group were enrolled. Questionnaires were filled in then, and other information was collected in 1980, '82, '86, '88 and 1992. This information showed the relationship between folate and multivitamin use and reduced colon cancer incidence ( Bandolier 60 ).

A new analysis [1] sought to pin down the relationship between coronary heart disease and exercise in women. In Japanese men, a study showed that regular walking decreased mortality ( Bandolier 50 ).

Study

Detailed information on physical activity was first collected in 1986 and updated in 1988 and 1992. This included various forms of vigorous and non-vigorous exercise, plus a walking history that included their walking pace: easy or casual (less than 2 mph), average (2.0 to 2.9 mph) or brisk (more than 3 mph) [note that 1 mph = 1.6 kph]. A weekly metabolic-equivalent (MET) was calculated for the various forms of activity. Total MET hours per week was then calculated.

Activity	MET per hour
Vigorous	more than 6
Nonvigorous	less than 6
Walking	2.5 to 4.5, depending on pace
a MET is the caloric need per Kg per hour of activity divided by the caloric need per Kg at rest

Outcomes The primary endpoint was coronary events defined as nonfatal myocardial infarction or death due to coronary disease occurring after 1986 and before mid-1994. There were 645 coronary events. The physical activity assessed in 1986 was used as the baseline. Results Information was grouped into quintiles of MET hours per week, with about 14,000 to 15,000 women in each quintile. The distribution of physical activity between the quintiles is shown in Figure 1. The mean of 15 MET hours per week in quintile 4, for instance, implies that a woman would walk briskly for about four hours per week. Women in the high MET quintiles were less likely to smoke, were leaner and had lower prevalences of diabetes, hypertension and hypercholesterolaemia than those in the lowest quintiles. Figure 1: MET hours per week for each quintile

When adjustment was made for these factors there remained a significant association between higher levels of total physical activity and reduced risk of a coronary event (Figure 2). There was a 34% reduced risk for the highest total activity quintile. Figure 2: Relative risk of coronary event for each quintile Significant reduction in quintiles 4 and 5

In women who took no vigorous exercise, brisk walking had a similar effect on reducing the risk of a coronary event (Figure 3). Using women who walked at a casual or easy pace as a baseline, women who walked briskly reduced their risk by 36%. Compared with sedentary women, women who walked briskly for 1 to 3 hours a week had a risk reduced by 30% (95% CI 5 to 49%) after allowing for other factors. Figure 3: Relative risk of coronary event by walking pace for women who did not take vigorous exercise

Comment This is another study linking increased physical activity to better health. Importantly this study is one of the biggest to examine the effects of exercise in women. The bottom line is that women who walk briskly or exercise vigorously for three hours a week or more can reduce their risk of heart disease. ImpAct 3 examined a visionary scheme for prescribing walking exercise. Bandolier 50 had reports of walking reducing coronary and all cause mortality in retired Japanese men in Hawaii, and of exercise reducing death rates in a Finnish twin study. The benefits of moderate exercise have been known for some time, and the evidence continues to accumulate. The size of the effects continues to impress, and just shows that evidence-based healthy living is something upon which we should concentrate more. Reference: JE Manson et al. A prospective study of walking as compared with vigorous exercise in the prevention of coronary heart disease in women. New England Journal of Medicine 1999 341: 650-8.