On the 1980 questionnaire, women were first asked about their recreational physical activity patterns. They were asked to report the average number of hours they spent each week during the past year on moderate and vigorous recreational activities including heavy gardening, vigorous sports, jogging, brisk walking or striding, bicycling, heavy housework, etc. On the 1982 questionnaire, women were asked a slightly different question: "For how many hours per week, on average, do you engage in activity strenuous enough to build up a sweat?" In 1986, 1988, 1992, and 1994, women were asked to report the average time spent per week during the past year on specific activities: walking or hiking outdoors, jogging (slower than 10 min/mile), running (10 min/mile or faster), bicycling (including use of a stationary bicycle), lap swimming, playing tennis or squash, and participating in calisthenics, aerobics, aerobic dance, or using a rowing machine. Each woman also reported her usual walking pace: easy (<2 mph), normal (2-2.9 mph), brisk (3-3.9 mph), or very brisk (≥4 mph). For 1980, 1982, 1986, 1988, 1992, and 1994, therefore, we had a measure of average hours per week of moderate or vigorous physical activity. (Walking done at an easy or normal pace was considered light activity, and was not counted in the measure of moderate or vigorous physical activity.) In 1986, 1988, 1992, and 1994, because we had information on specific activities, we were able to create a variable representing average hours per week of vigorous-only physical activity. Vigorous physical activity was defined as any activity with an assigned metabolic equivalent task value21 of 6.0 or greater; in these data, these activities included jogging, running, bicycling, swimming, tennis and/or squash, calisthenics, aerobics, and use of a rowing machine.