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