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.