Environmental tobacco smoke exposure as a risk factor for infections in infancy

This prospective observational study investigated the effect of environmental tobacco smoke (ETS) on frequency and severity of common infantile infections. In a representative sample of 926 infants, parental smoking was recorded at months 1 and 9 postpartum, and all infantile infectious episodes were recorded at 1, 3, 6, 9 and 12 months postpartum. Both parents were regular smokers all through the first year in 107 (11.6%), at least one smoked regularly or occasionally in 492 (53.1%), and parents did not smoke at all in 327 (35.3%) families. Among mothers, 168 (18.1%) smoked perinatally. Infantile ETS exposure was associated with increased frequency of total infectious episodes (p = 0.025) and hospitalizations for infection (p = 0.007). In ETS exposed infants, birth in autumn and presence of siblings contributed to increased frequency of most infections and of hospital admissions for infection. By contrast, exclusive breastfeeding protected against the effect of ETS on total infantile infections (OR 0.982, 95% CI 0.965-0.999; p = 0.036), hospital admissions for infection (OR 0.980, 95% CI 0.961-0.999; p = 0.036) and thrush (OR 0.973, 95% CI 0.951-0.996; p = 0.022). Our findings point to harmful effect of ETS on infantile health and further suggest that this effect may be enhanced or diminished by other factors. ETS should be regarded as a preventable risk factor for infections in infancy.