Background: Environmental tobacco smoke (ETS) increases the risk of heart disease in several epidemiological studies although the methods of assessing exposure have been incomplete. We determined the prevalence of ETS from various sources, and examined the association between ETS and the risk of myocardial infarction. Methods: A hospital-based case-control study of myocardial infarction was conducted from 1980 to 1990 by interviewing 114 case patients and 158 control subjects. Results: Among controls, the sources of ETS were the workplace (56%), childhood exposure (66%), home adult exposure (48%), car exposure (20%) and from trains or other surface transportation (4%). Compared to never smokers, the odds ratio (OR) for exposure to ETS during childhood was 0.97 (95% confidence intervals [Cl]: 0.53-1.46) for men and 0.92 (95% Cl: 0.5-1.86) for women. The adjusted OR associated with adult exposure was 1.5 (95% Cl: 0.9-2.6), although no trend was observed with the number of years of exposure. Women who were exposed to ETS in automobiles had an increased but non-significant risk (OR = 2.8, 95% Cl: 0.9-8.0). Conclusions: Exposure to ETS comes from a variety of sources besides the spouse including parents, workplace employees and motorists. Exposure to ETS during childhood is not associated with an increased risk of heart disease. However, ETS exposure during adulthood increased the risk of myocardial infarction approximately 50% in this data although the findings were not statistically significant.
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