American journal of diseases of children (1911)
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Bronchiolitis is a common lower respiratory tract illness in infants and has substantial acute morbidity and sequelae. To identify risk factors for bronchiolitis, a case-control study was conducted in which 53 subjects who had bronchiolitis were matched with two controls who had no bronchiolitis in infancy. In multivariate analysis, direct effects of passive smoking and older siblings achieved statistical significance. ⋯ Among infants without a family history of asthma, bronchiolitis may develop in 46% of infants if there is both an older sibling and exposure to smoke. Exposure of infants to cigarette smoke might diminish more rapidly if clinicians and parents were aware of such high risks. Efforts to reduce morbidity from bronchiolitis in infants might best be directed at the reduction of smoking in families with previous children, particularly if there is a family history of asthma, and at methods that protect infants from respiratory virus carried by siblings.