Regular Smoking and Asthma Incidence in Adolescents.
Am J Respir Crit Care Med. 2006 Sep 14 Gilliland FD, Islam T, Berhane K, Gauderman WJ, McConnell R, Avol E, Peters JM. Department of Preventive Medicine, University of Southern California, Keck School of Medicine, Los Angeles, CA, USA.
Rationale: Although involuntary exposure to maternal smoking during the in utero period and to secondhand smoke are associated with occurrence of childhood asthma, few studies have investigated the role of active cigarette smoking on asthma onset during adolescence.
Objectives: To determine whether regular smoking is associated with the new onset of asthma during adolescence.
Methods: We conducted a prospective cohort study among 2609 children with no lifetime history of asthma or wheezing who were recruited from fourth and seventh grade classrooms and followed annually in schools in 12 southern California communities. Regular smoking was defined as smoking at least 7 cigarettes per day on average over the week before and 300 cigarettes in the year before each annual interview. Incident asthma was defined using new cases of physician-diagnosed asthma.
Measurements and Main Results: Regular smoking was associated with increased risk of new onset asthma. Children who reported smoking 300 or more cigarettes per year had a relative risk (RR) of 3.9 [95% confidence interval (95% CI): 1.7-8.5] for new onset asthma compared to nonsmokers. The increased risk from regular smoking was greater in non-allergic than allergic children. Regular smokers who were exposed to maternal smoking during gestation had the largest risk from active smoking (RR: 8.8, 95% CI: 3.2-24.0).
Conclusions: Regular smoking increased risk for asthma among adolescents, especially for nonallergic adolescents and those exposed to maternal smoking during the in utero period.