Tobacco smoke exposure in early life and adolescence in relation to lung function

Maternal smoking during pregnancy is associated with impaired lung function among young children, but less is known about long-term effects and the impact of adolescents' own smoking. We investigated the influence of maternal smoking during pregnancy, secondhand smoke exposure and adolescent smoking on lung function at age 16 years.The BAMSE (Barn/Child, Allergy, Milieu, Stockholm, Epidemiology) birth cohort collected information on participants' tobacco smoke exposure through repeated questionnaires, and measured saliva cotinine concentrations at age 16 years. Participants performed spirometry and impulse oscillometry (IOS) at age 16 years (n=2295).Exposure to maternal smoking during pregnancy was associated with reduced forced expiratory volume in 1 s (FEV₁)/forced vital capacity (FVC) ratio of -1.1% (95% CI -2.0 to -0.2%). IOS demonstrated greater resistance at 5-20 Hz (R_5-20) in participants exposed to maternal smoking during pregnancy. Adolescents who smoked had reduced FEV₁/FVC ratios of -0.9% (95% CI -1.8 to -0.1%) and increased resistance of 6.5 Pa·L^-1·s (95% CI 0.7 to 12.2 Pa·L^-1·s) in R_5-20 Comparable associations for FEV₁/FVC ratio were observed for cotinine concentrations, using ≥12 ng·mL^-1 as a cut-off for adolescent smoking.Maternal smoking during pregnancy was associated with lower FEV₁/FVC ratios and increased airway resistance. In addition, adolescent smoking appears to be associated with reduced FEV₁/FVC ratios and increased peripheral airway resistance.