Environmental tobacco smoke and myocardial infarction among never-smokers in the Stockholm Heart Epidemiology Program (SHEEP)

An increased risk for myocardial infarction (,Ml) related to environmental tobacco smoke (ETS). exposure has previously been reported, but several asp ects. of the association are still uncertain. We studied the MI risk associ ated with ETS exposure among 334 nonfatal never-smoking MI cases and 677 po pulation controls, 45-70 years of age, in Stockholm County. A postal questi onnaire with a telephone follow-up provided information on ETS exposure and other potential risk factors for MI. After adjustment for age, gender, hos pital catchment area, body mass index, socioeconomic status, job strain, hy pertension, diet, and diabetes mellitus, the odds ratio for MI was 1.58 (95 % confidence interval = 0.97-2.56) for an average daily exposure of 20 ciga rettes or more from the spouse. Combined exposure from spouse and work show ed an increasing odds ratio for MI, up to 1.55 (95% confidence interval = 1 .02-2.34) in the highest category of weighted duration, that is, more than 90 "hour-years" of exposure (1 "hour-year" = 365 hours, or 1 hour per day f or 1 year). In addition, more recent exposure appeared to convey a higher r isk. Our data confirm an increased risk of MI from exposure to ETS and sugg est that intensity of spousal exposure, combined exposure from spouse and w ork, and time since last exposure are important.