A number of previous studies conducted in developed countries show a relationship between higher levels of physical activity and lower risks of cardiovascular disease.  In a case-control study of 10,043 cases of first myocardial infarction (heart attack) and 14,217 controls who did not report previous angina or physical disability, Claes Held, from Uppsala University (Sweden), and colleagues assessed leisure-time and occupational physical activity.   Study subjects who had a heart attack were more likely to be sedentary during leisure time and work, as compared to controls. For leisure-time activity the odds of a heart attack were lower with as little as mild-exertion exercise, with beneficial effects seen in as little as 30 minutes of exercise per week. For occupational activity, both light and moderate physical activity associated with lower odds of heart attack, as compared to being sedentary; strenuous work activity was not related to an increased risk of heart attack, in large part because such activity did not involve extended aerobic exertion. The team also explored various markers of sedentary behavior. They found that owning a car, radio or stereo, and a home was significantly associated with the risk of heart attack. Owning a television was of borderline significance.  Observing that: "”Leisure-time [physical activity] and mild-to-moderate occupational [physical activity], but not heavy physical labour, were associated with a reduced risk,” the study authors warn that: "ownership of a car and TV was associated with an increased risk of [myocardial infarction] across all economic regions.”