Table 4.

Effect of demographic and clinical predictors on eventual bronchiolitis episodes >1 day in multivariate analysis

Clinical and demographic predictors	Beta	Odds Ratio (95% CI)
Sex (Male)	0.38	1.47 (1.40–1.54)
Racea
White	1.00	reference
African-American	0.01	1.01 (0.93–1.10)
Asian	−0.17	0.85 (0.79–0.90)
Hispanic	0.13	1.13 (1.07–1.20)
Other/unknown	−0.11	0.89 (0.82–0.98)
Gestational age, wk
32–33	0.58	1.79 (1.53–2.09)
34–36	0.43	1.53 (1.41–1.66)
37	0.18	1.20 (1.10–1.31)
38–40	1.00	reference
≥41	−0.11	0.90 (0.84–0.96)
Small for gestational ageb	0.32	1.37 (1.16–1.61)
Congenital anomaly presentc	0.15	1.17 (1.08–1.27)
Family history of asthmad
None	1.00	reference
Father only	0.24	1.27 (1.08–1.50)
Mother only	0.45	1.56 (1.41–1.72)
≥1 sibling <5 y of age in home	0.37	1.45 (1.39–1.52)
O2 exposure and BPDe
No O2 exposure, no BPD	1.00	reference
<200 hr O2, no BPD	0.22	1.25 (1.12–1.39)
≥200 hr O2, no BPD	0.88	2.41 (1.89–3.07)
BPDf	0.69	1.99 (1.13–3.49)
Maternal age, y
<18	0.03	1.03 (0.85–1.26)
18–34	1.00	reference
≥35	−0.09	0.91 (0.86–0.96)

BPD = bronchopulmonary dysplasia.

^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.

^bBased on the algorithm of Brenner WE, et al. [19].

^cSee text for list of included International Classification of Diseases codes.

^dAscertained by electronic scanning of parental records, which included encounters and diagnoses identified in the Significant Problem List by the parent’s physician.

^eOxygen exposure, in hours, during the birth hospitalization. See text for details.

^fAll infants with BPD had ≥200 hours of oxygen exposure during the neonatal period.