Background: Scientific evidence shows that physically active people are protected from developing acute myocardial infarction (MI). However, the effect of the intensity, duration and type of activity remains unclear.
Objective: To evaluate the relation between physical activity and MI, according to different intensity levels and types, we conducted a community-based case-control study, based on the Risk of Coronary Heart Disease (EPIcardis) study.
Methods: We evaluated 381 consecutive cases of first MI (297 males; 84 females) and 726 community controls (310 males; 416 females), older than 39 years, selected by random digit dialing (70% participation rate among the controls). Data were collected using a structured questionnaire. For evaluation of physical activity, the questionnaire assessed all professional and leisure-time activities, specifying the type of exercise and the time spent in each activity. Activities were grouped according to intensity using energy expenditure at rest as the baseline (1.0 MET): very light (1.5 MET), light (2.5 MET), moderate (5.0 MET) and strenuous (7.0 MET). Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated using unconditional logistic regression and separate models for each sex.
Results: Among men, after adjusting for age, education, family history of MI, energy intake and smoking, the OR (95% CI) were 0.51 (0.29-0.91), 0.36 (0.19-0.68), 0.53 (0.30-0.93), and 0.68 (0.39-1.20), for increasing quintiles of activity (p for trend = 0.199). Among women, after adjusting for the same variables plus parity and menopausal status, the OR (95% CI) were 0.51 (0.25-1.03), 0.37 (0.17-0.83), and 0.34 (0.14-0.83), for increasing quartiles of activity (p for trend = 0.006). We found a protective effect of leisure-time physical activity in men (p for trend < 0.001) and in women (p for trend = 0.038). In men, the U-shaped effect described for total physical activity was also found for occupational activities.
Conclusions: The present study supports an independent protective effect of leisure-time physical activity, but not of occupational activities, for risk of myocardial infarction.