Asthma diagnosis in a child and cessation of smoking in the child’s home: the PIAMA birth cohort

Second hand smoke (shs) exposure is associated with increased incidence and severity of childhood asthma. we investigated whether, in turn, asthma diagnosis in a child is associated with cessation of smoking exposure in the child’s home. in the piama birth cohort (n=3963), parents reported on smoking in their home and on asthma diagnosis in their child, annually from birth to 8 years. we used generalized estimating equations to assess the association between asthma diagnosis in a child and cessation of smoking in the child’s home. among children with residential shs exposure, smoking stopped in 23.7% of the homes of children with newly diagnosed asthma as compared with 16.2% of the homes of children without asthma diagnosis (p=0.014). for children with an asthma diagnosis, the relative risk of smoking cessation in their home was 1.36 (one-sided 95% confidence interval: 1.09, inf.) and changed little after adjustment for maternal education, parental allergy and child’s age. in most smokers’ households (76.3%), smoking continued when the child got an asthma diagnosis. nevertheless, an asthma diagnosis in the child increased the probability of a smoke-free home for the child and its parents and siblings. cross-sectional associations between shs exposure and asthma may underestimate true associations, because exposure may have been reduced following diagnosis of the disease.