Parental smoking and other risk factors for wheezing bronchitis in children

A population-based case-control study was performed to investigate etiologic factors for wheezing bronchitis and asthma in children up to four years of age. A total of 199 children hospitalized for the first time with these diagnoses at a major hospital in Stockholm in 1986–1988 constituted the cases, 351 children from the catchment area of the hospital were used as controls. Information on known and suspected risk factors was obtained through home interviews with a parent. Parental smoking was associated with a relative risk of 1.8 (95% confidence interval 1.3 – 2.6) corresponding to a population attributable proportion of 27%. The strongest association was seen for maternal smoking and children below 18 months of age. Other major risk factors included atopic heredity, recurrent upper respiratory tract infections and breast-feeding less than 3 months, which appeared to interact multiplicatively with parental smoking. The environmental factors had a stronger influence in the youngest age group, and the overall attributable proportion associated with parental smoking, short breast-feeding period and exposure to pets in the household was 43%. It is clear that successful primary prevention could dramatically reduce the incidence of wheezing bronchitis in children.