PURPOSE OF THE STUDY.
To study the independent and joint effects of prenatal smoking and low birth weight (LBW) on childhood asthma.
The study included asthmatic 11- to 12-year-old children in Sweden (N = 3389).
Children were studied by questionnaire survey as part of the International Study of Asthma and Allergy in Childhood (ISAAC). A subset of 2121 children also underwent skin-prick testing.
Mean birth weight was 3360 g in children exposed to prenatal smoking and 3571 g in nonexposed children (P < .001). The association of prenatal smoking with physician-diagnosed asthma was stronger in LBW children (risk ratio: 8.8 [95% confidence interval: 2.1–38]) than in normal birth weight children (risk ratio: 1.3 [95% confidence interval: 1.0–1.8]). LBW alone was not an independent predictor of asthma.
There is a strong interaction of LBW and prenatal smoking on the risk of physician-diagnosed asthma, which is observed even after adjusting for known risk factors including allergic sensitization.
This report highlights the observation that the combination of LBW and prenatal smoking increases the risk of physician-diagnosed asthma sixfold versus either LBW (no effect) or prenatal smoking (weak effect) alone. The authors speculated that smoke-induced oxidative stress in underdeveloped airways (caused by impaired fetal growth) might lead to increased asthma risk. In this regard, it has been shown that smoke exposure interacts with ADAM33 polymorphisms in a way that adversely affects lung function and hyperresponsiveness.
- Copyright © 2011 by the American Academy of Pediatrics