Parental smoke exposure before age 15 and offspring asthma trajectories from ages 7 to 53

Background and objective Paternal passive smoke exposure before age 15 years was associated with offspring childhood asthma, but its association with asthma beyond childhood had not been investigated. We aimed to investigate such long-term association. Methods Data were from 1078 father-offspring and 1537 mother-offspring pairs from the Tasmanian Longitudinal Health Study. Offspring (probands of the original cohort) completed asthma surveys at ages 7, 13, 18, 30, 43, 50, and 53. Life-course asthma trajectories were developed using group-based trajectory modelling. Parents self-reported their own passive smoke exposure before age 15. Multinomial logistic regressions assessed associations between parental passive smoke exposure and offspring asthma trajectories. Active parental smoking, offspring sex, childhood respiratory illnesses, and subsequent active smoking were evaluated for mediations and interactions. Results Paternal passive smoke exposure before 15 was associated with Early-Onset Adult-Remitting asthma trajectory (adjusted multinomial odds ratio [aMOR]=2.53 [95%CI: 1.09–5.85]) in offspring, but not persistent asthma trajectories. Maternal passive smoke exposure before 15 was associated with Early-Onset Adult-Remitting asthma trajectory in offspring who were also exposed to childhood passive smoke (aMOR=4.30 [1.01–18.40]; p -interaction =0.044). The observed associations were partly mediated through active parental smoking or offspring childhood respiratory illnesses (each <10%). Conclusions This study identified a novel association between parental passive smoke exposure before 15 and Early-Onset Adult-Remitting asthma trajectory in offspring, which is related to subsequent COPD. These findings suggest that in parents inevitably exposed to passive smoke during childhood/puberty, asthma risk in future generations associated with such exposure may be lower if parents avoid smoking around children.