Regular smoking and asthma incidence in adolescents.
BACKGROUND
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.


OBJECTIVE
To determine whether regular smoking is associated with the new onset of asthma during adolescence.


METHODS
We conducted a prospective cohort study among 2,609 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 seven 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.


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 with nonsmokers. The increased risk from regular smoking was greater in nonallergic than in 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.
Gilliland
Frank D
FD
Department of Preventive Medicine, Keck School of Medicine of USC, 1540 Alcazar Street, CHP 236, Los Angeles, CA 90033, USA. gillilan@usc.edu
Islam
Talat
T
Berhane
Kiros
K
Gauderman
W James
WJ
McConnell
Rob
R
Avol
Edward
E
Peters
John M
JM
D000293:Adolescent; D017668:Age of Onset; D001249:Asthma / Q000453:epidemiology*; D002140:California / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D018811:Maternal Exposure; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment; D012907:Smoking / Q000453:epidemiology* / Q000503:physiopathology; D014028:Tobacco Smoke Pollution
D014028:Tobacco Smoke Pollution