Both environmental tobacco smoke and personal smoking is related to asthma and wheeze in teenagers

Background Environmental tobacco smoke (ETS) has been reported as a significant risk factor for childhood asthma. Among adults, personal smoking is a major cause of respiratory symptoms and diseases. The effects of these exposures on the prevalence of asthma and wheeze among teenagers are less well known. Objective The aim was to study the independent and combined effects of ETS and personal smoking on the prevalence of asthma and wheeze in teenagers. Methods A longitudinal study of asthma and allergic diseases in schoolchildren has been in progress in Northern Sweden since 1996. All children aged 7-8 years in three municipalities were invited and 3430 (97%) participants have been followed by annual questionnaires. At the age 16-17 years, 82% of the initial participants took part in the 2005 survey. Results Prevalence of physician-diagnosed asthma, ever wheeze and current wheeze was significantly higher among those exposed to maternal ETS and among daily smokers. In multivariate analyses, maternal ETS was a significant risk factor for physician-diagnosed asthma and ever wheeze (OR 1.3-1.5) and personal daily smoking for current wheeze (OR 2.0). ORs for asthma and ever wheeze were highest among daily smokers who were also exposed to maternal ETS with ORs of 1.7 and 2.5, respectively. A significant dose-response association between number of cigarettes/day and the prevalence of wheeze was also found. Conclusions Both ETS and personal smoking were significantly related to asthma and wheeze in teenagers. Maternal ETS exposure was associated with lifetime symptoms, but daily smoking among the teenagers was more strongly related to current symptoms.