Exposure to tobacco smoke prenatally and during infancy and risk of hearing impairment among children in Japan: A retrospective cohort study.

BACKGROUND: Previous studies of the association between tobacco smoke and hearing loss in children are limited, involve small samples and are cross-sectional. We investigated the association of maternal smoking during pregnancy and exposure to tobacco smoke at age 4 months with hearing impairment at age 3 years in children.

METHODS: This population-based retrospective cohort study included 50 734 children born between 2004 and 2010 in Kobe City, Japan. Smoking during pregnancy and exposure to tobacco smoke at 4 months was measured using parent-reported questionnaires. Hearing impairment was determined by the whispered voice test.

RESULTS: Of the included children, 3.8% were exposed to smoking only during pregnancy; 3.9% were exposed only to second-hand smoke at 4 months; and 0.9% were exposed to tobacco smoke during pregnancy and at 4 months. The prevalence of hearing impairment at age 3 years was 4.6%. Compared with children not exposed to tobacco smoke prenatally and at 4 months, the risk of hearing impairment was elevated in children exposed to only maternal past smoking during pregnancy (RR 1.26, 95% CI 1.13, 1.40), only second-hand smoke at 4 months (RR 1.30, 95% CI 1.07, 1.56), only smoking during pregnancy (RR 1.68, 95% CI 1.42, 2.00) and smoking during pregnancy and second-hand smoke at 4 months (RR 2.35, 95% CI 1.79, 3.10).

CONCLUSIONS: Exposure to tobacco smoke prenatally and postnatally was associated with hearing impairment in children. A prevention of smoking before and during pregnancy and exposure to second-hand smoke postnatally may reduce hearing impairment risk in children.