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Background The role of walking, as compared with vigorous exercise, in the prevention of coronary heart disease remains controversial, and data for women on this topic are sparse. Methods We prospectively examined the associations between the score for total physical activity, walking, and vigorous exercise and the incidence of coronary events among 72,488 female nurses who were 40 to 65 years old in 1986. Participants were free of diagnosed cardiovascular disease or cancer at the time of entry and completed serial detailed questionnaires about physical activity. During eight years of follow-up, we documented 645 incident coronary events (nonfatal myocardial infarction or death from coronary disease). Results There was a strong, graded inverse association between physical activity and the risk of coronary events. As compared with women in the lowest quintile group for energy expenditure (expressed as the metabolic-equivalent [MET] score), women in increasing quintile groups had age-adjusted relative risks of 0.77, 0.65, 0.54, and 0.46 for coronary events (P for trend <0.001). In multivariate analyses, the inverse gradient remained strong (relative risks, 0.88, 0.81, 0.74, and 0.66 for women in increasing quintile groups as compared with those in the lowest quintile group; P for trend=0.002). Walking was inversely associated with the risk of coronary events; women in the highest quintile group for walking, who walked the equivalent of three or more hours per week at a brisk pace, had a multivariate relative risk of 0.65 (95 percent confidence interval, 0.47 to 0.91) as compared with women who walked infrequently. Regular vigorous exercise (»6 MET) was associated with similar risk reductions (30 to 40 percent). Sedentary women who became active in middle adulthood or later had a lower risk of coronary events than their counterparts who remained sedentary. Conclusions These prospective data indicate that brisk walking and vigorous exercise are associated with substantial and similar reductions in the incidence of coronary events among women.

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