Meta-analysis on the association between environmental tobacco smoke (ETS)exposure and the prevalence of lower respiratory tract infection in early childhood

The aim of this study was to obtain quantitative information from published data on the association between environmental tobacco smoke (ETS) exposure and the prevalence of serious lower respiratory tract infections (LRTI) in infancy and early childhood. We identified 21 relevant publications on the relation between ETS and the prevalence of serious LRTI by reviewing refer ence lists in relevant reports and by conducting manual and computer search es (Medline database; Dissertation abstracts index of Xerox University Micr ofilms) of published reports between 1966 and 1995. Thirteen studies were i ncluded in a quantitative overview using random effects modeling to derive pooled odds ratios. Sensitivity analyses were conducted to test the decision rules used in extr acting odds ratio data. The results of community and hospital studies are b roadly consistent and show that the child of a parent who smokes is at appr oximately twice the risk of having a serious respiratory tract infection in early life that requires hospitalization. This association was pronounced in children younger than age two and diminished after the age of two. The c ombined odds ratio for hospitalization for lower respiratory tract infectio ns in infancy or early childhood is 1.93 (95% CI 1.66-2.25); the combined o dds ratio of prevalence of serious LRTI at age less than 2 years, between 0 and 6 years, and between 3 and 6 years were 1.71 (95% CI 1.33-2.20); 1.57 (1.28-1.91), and 1.25 (0.88-1.78), respectively. There was no evidence of h eterogeneity across the studies in these combined odds ratios. We conclude that this meta-analysis provides strong evidence that exposure to ETS cause s adverse respiratory health outcomes such as either a serious LRTI or hosp italization for LRTI. New public health campaigns are urgently needed to di scourage smoking in the presence of young children. Pediatr Pulmonol, 1999; 27:5-13. (C) 1999 Wiley-Liss, Inc.