Associations of timing, level, and pattern of secondhand smoke exposure with early alcohol initiation: A cohort study

Background: Few studies explored the longitudinal link between early-life secondhand smoke (SHS) exposure and later alcohol initiation despite its risk for child behavioral difficulties. We examined the associations of the timing, level, and pattern of SHS exposure from pregnancy to childhood with early alcohol initiation and evaluated the sex differences in these associations.Methods: Data were from 16,440 participants of the Taiwan Birth Cohort Study conducted when the children were aged 6 months, 18 months, 3 years, 5.5 years, 8 years, and 12 years. Group-based trajectory modeling was applied to identified patterns of SHS exposure. A series of multiple logistic regression were conducted to examine study hypotheses.Results: Exposure to prenatal SHS was associated with an increased risk of early alcohol initiation (adjusted odds ratio [aOR] = 1.17, 95% confidence interval [CI] = 1.06, 1.30). Compared with the adolescents with a persistent low-exposure trajectory, those who exhibited prenatal-high-decreasing (aOR = 1.18, 95% CI = 1.04, 1.35) or persistent-high-exposure (aOR = 1.27, 95% CI = 1.12, 1.45) patterns exhibited increased risks of early alcohol initiation. Those with higher cumulative levels of SHS exposure also exhibited an increased risk of early alcohol initiation (aOR = 1.03, 95% CI = 1.01, 1.04). Sex differences were also observed.Conclusions: Varying timing, levels, and longitudinal patterns of SHS exposure during early life had differential effects on early alcohol initiation, with the effects differing by sex. Targeting SHS exposure while considering the nature of exposure and sex differences could help prevent and curb alcohol use in adolescents.