Risk factors for bronchiolitis-associated deaths among infants in the United States

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Abstract
Background. Risk factors for bronchiolitis deaths have not been described on a national level. We examined the epidemiology of and identified risk factors for bronchiolitis-associated deaths among infants in the United States. Methods. Multiple cause-of-death and linked birth/infant death data for 1996 through 1998 were used to examine bronchiolitis-associated infant deaths. Risk factors were assessed by comparing infants who died with bronchiolitis and surviving infants. Results. During 1996 through 1998 there were 229 bronchiolitis infant deaths, resulting in an average annual infant mortality rate of 2.0 per 100 000 live births. The majority (55%) of infant deaths occurred among infants ages 1 through 3 months. The bronchiolitis mortality rate was highest among infants weighing <1500 g at birth (VLBW) as compared with infants weighing 1500 to 2499 g (LBW) and ≥2500 g at birth (29.8, 6.4 and 1.3 per 100 000 live births, respectively). Sixty-three percent of bronchiolitis deaths were among infants weighing ≥2500 g. VLBW and LBW infants remained at an increased risk of dying with bronchiolitis after controlling for other risk factors. Other risk factors included increasing birth order, low 5-min Apgar score, young maternal age, unmarried mother and tobacco use during pregnancy. Conclusions. VLBW and LBW infants are at increased risk of dying with bronchiolitis, even when taking into account other risk factors. Although infants weighing <2500 g at birth are at increased risk for dying with bronchiolitis, the majority of bronchiolitis deaths occur among infants of normal birth weight.