Smoking status was investigated using the following structured questionnaire: “Have you smoked at least 100 cigarettes in your entire life?”; “Do you now smoke cigarettes?” Passive smoking status was investigated using the following question: “Does anyone who lives here smoke cigarettes, cigars, or pipes anywhere inside this home?”.All participants were categorized according to smoking status, consisting of never-smoker, former smokers, and current smokers, and the presence of passive smoking. We calculated smoking pack-years to estimate cumulative exposure to smoking. In addition, we used the blood cotinine concentration (ng/mL) to estimate the extent of current exposure to tobacco smoke.
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