Active, passive, and electronic cigarette smoking is associated with asthma in adolescents

The present study investigated the associations of active, passive, and electronic cigarette (E-cigarette) smoking with asthma in Korean adolescents. We used the cross-sectional study of Korea Youth Risk Behavior Web-based Survey conducted in 2011, 2012 and 2013. Active smoking was classified into 4 groups (0 days, 1-5 days, 6-19 days, and >= 20 days a month). Passive smoking was also categorized into 4 groups (0 days, 1-2 days, 3-4 days, and >= 5 days a week). E-cigarette was defined as yes or no in the last 30 days. Age, sex, obesity, region of residence, economic level, and parental educational level were adjusted for as confounders. Smoking variables were adjusted for one another. Adjusted odd ratios (AORs) and 95% confidence intervals (CIs) were calculated using multiple logistic regression analysis with complex sampling. In total, 2.3% (4,890/216,056) of participants reported asthma in the past 12 months. Active smoking was significantly associated with asthma (AOR [95% CI] of smoking >= 20 days/month = 1.57 [1.38-1.77], P < 0.001). Passive smoking was also related with asthma (AOR [95% CI] of smoking >= 5 days/week = 1.40 [1.28-1.53], P < 0.001). E-cigarette showed positive relation with asthma, although the effects of past smoking history could not be excluded (AOR [95%CI] = 1.12 [1.01-1.26], P = 0.027).