title: Physical activity and risk of myocardial infarction after the fourth decade of life.
abstract: 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.
authors.affiliation: Serviço de Higiene e Epidemiologia, Faculdade de Medicina do Porto, Porto, Portugal. carlal@med.up.pt
authors.forename: Carla
authors.initials: C
authors.lastname: Lopes
authors.forename: Ana Cristina
authors.initials: AC
authors.lastname: Santos
authors.forename: Ana
authors.initials: A
authors.lastname: Azevedo
authors.forename: Maria Júlia
authors.initials: MJ
authors.lastname: Maciel
authors.forename: Henrique
authors.initials: H
authors.lastname: Barros
mesh_terms: D000328:Adult; D000367:Age Factors; D016022:Case-Control Studies; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity; D009203:Myocardial Infarction / Q000453:epidemiology*; D012307:Risk Factors