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Table 1 Demographic and clinical characteristics of the main cohort and subgroups

From: Frequency, duration and predictors of bronchiolitis episodes of care among infants ≥32 weeks gestation in a large integrated healthcare system: a retrospective cohort study

  All infants, n (%) Infants with any bronchiolitis episode before age 2 y, n (%) Infants with any bronchiolitis episode before age 2 y lasting >1 d, n (%)
Sex (Male) 63,054 (51.2) 11,730 (58.7) 5,206 (60.1)
Racea
  White 52,609 (42.7) 8,305 (41.6) 3,754 (43.4)
  African-American 10,374 (8.4) 1,866 (9.3) 740 (8.6)
  Asian 24,977 (20.3) 3,599 (18.0) 1,505 (17.4)
  Hispanic 25,619 (20.8) 4,704 (23.6) 2,047 (23.6)
  Other/unknown 9,685 (7.9) 1,494 (7.5) 612 (7.1)
Gestational age, wk
  32–33 1,649 (1.3) 406 (2.0) 218 (2.5)
  34–36 7,969 (6.5) 1,622 (8.1) 830 (9.6)
  37 7,855 (6.4) 1,400 (7.0) 632 (7.3)
  38–40 86,708 (70.3) 13,701 (68.6) 5,834 (67.4)
  ≥41 19,083 (15.5) 2,839 (14.2) 1,144 (13.2)
Small for gestational ageb 1,763 (1.4) 323 (1.6) 168 (1.9)
Congenital anomaly presentc 8,646 (7.0) 1,642 (8.2) 764 (8.8)
Family history of asthmad
  None 116,763 (94.7) 18,618 (93.2) 8,011 (92.5)
  Father only 1,824 (1.5) 336 (1.7) 160 (1.9)
  Mother only 4,561 (3.7) 989 (5.0) 476 (5.5)
  Both parents 116 (0.1) 25 (0.1) 11 (0.1)
≥1 sibling <5 y of age in home 44,235 (35.9) 8,405 (42.1) 3,801 (43.9)
O2 exposure and BPDe
  No O2 exposure, no BPD 118,599 (96.2) 18,941 (94.9) 8,126 (93.9)
  <200 hr O2, no BPD 4,117 (3.3) 867 (4.3) 427 (4.9)
  ≥200 hr O2, no BPD 466 (0.4) 138 (0.7) 89 (1.0)
  BPDf 82 (0.1) 22 (0.1) 16 (0.2)
  1. BPD = bronchopulmonary dysplasia.
  2. aClassification of race/ethnicity in this study was based on the race of infants' mothers, as self-reported to the birth certificate clerk interviewing them at the Kaiser Permanente hospitals described in this study. Race was assessed in this study because of the well-known differences in RSV severity by race.
  3. bBased on the algorithm of Brenner WE, et al. [19].
  4. cSee text for list of included International Classification of Diseases codes.
  5. dAscertained by electronic scanning of parental records, which included encounters and diagnoses identified in the Significant Problem List by the parent’s physician.
  6. eOxygen exposure, in hours, during the birth hospitalization. See text for details.
  7. fAll infants with BPD had ≥200 hours of oxygen exposure during the neonatal period.