Environmental Tobacco Smoke and Middle Ear Disease in Pre-schoolers • 429

Abstract

According to the U.S. EPA, there is some evidence for an association between exposure to environmental tobacco smoke (ETS) and middle ear disease(MED) in young children. However the evidence is derived largely from unvalidated measures in hospital-based studies. Methods. Cases and controls were identified through a population-based probability sample of 1320(81% response) first-grade students in 35 Calgary schools. Parents of 625 children meeting case (n=227) or control (n=398) definitions were interviewed by telephone for exposure history in three periods to age 6. Adequacy of exposure and disease measures were assessed using hair cotinine analysis and physician chart reviews for 92. Results. A history of persistent or recurrent MED was very prevalent (23.9%) in the sample. Relationships were found between MED and ≥2 household smokers, crude OR=1.85 (1.15 - 2.97);≥10 cigarettes smoked by the mother per day, crude OR=1.68(1.12-2.52); and≥10 cigarettes smoked in total in the household per day, crude OR=1.40(.98-2.00) in the first 3 years of life. In logistic regression modelling, these effects persisted after adjusting for childcare, infant feeding, SES, maternal education, prenatal ultrasound exams, and health services utilization, OR=1.88(1.12-3.14) for ≥ 2 household smokers. A pattern suggestive of dose-response was found for maternal cigarettes per day(Mantel-Haenszel trend test p =.05). The primary association was stronger in the highest response schools (OR=2.76(0.44-18.35)), suggesting bias toward the null. Mean current hair cotinine levels were higher for children living in homes with ≥ 1 smoker vs. none (.51 vs..30 ng/mg, p=.01). There was fair agreement (75.3%) between physician records and parent report of disease history where records were complete, but some misclassification bias toward the null is likely. Conclusions. ETS is an important risk factor for MED in urban pre-schoolers, even in relatively affluent populations. Based on the effect found in this study, the proportion of disease among urban children attributable to high houshold ETS exposure (etiologic fraction) is 13.01(6.28-19.74)%.