Aims To evaluate the association between occupational and leisure-time physical activity (PA), ownership of goods promoting sedentary behaviour, and the risk of myocardial infarction (MI) in different socio-economic populations of the world. Studies in developed countries have found low PA as a risk factor for cardiovascular disease; however, the protective effect of occupational PA is less certain. Moreover, ownership of goods promoting sedentary behaviour may be associated with an increased risk.
Methods In INTERHEART, a case–control study of 10 043 cases of first MI and 14 217 controls who did not report previous angina or physical disability completed a questionnaire on work and leisure-time PA.
Results Subjects whose occupation involved either light [multivariable-adjusted odds ratio (OR) 0.78, confidence interval (CI) 0.71–0.86] or moderate (OR 0.89, CI 0.80–0.99) PA were at a lower risk of MI, whereas those who did heavy physical labour were not (OR 1.02, CI 0.88–1.19), compared with sedentary subjects. Mild exercise (OR 0.87, CI 0.81–0.93) as well as moderate or strenuous exercise (OR 0.76, CI 0.69–0.82) was protective. The effect of PA was observed across countries with low, middle, and high income. Subjects who owned both a car and a television (TV) (multivariable-adjusted OR 1.27, CI 1.05–1.54) were at higher risk of MI compared with those who owned neither.
Conclusion Leisure-time PA and mild-to-moderate occupational PA, but not heavy physical labour, were associated with a reduced risk, while ownership of a car and TV was associated with an increased risk of MI across all economic regions.