TABLE 2

Multivariate Results for Bronchiolitis Among Infants in the Georgia Air Basin in 1999–2002

VariableAdjusted Hazard Rate Ratio (95% Confidence Interval)
Outpatient or Inpatient Case DefinitionInpatient Case Definition
Gender
    Female1.001.00
    Male1.38 (1.33–1.43)1.49 (1.34–1.64)
Maternal age
    20–29 y1.001.00
    >29 y0.81 (0.78–0.84)0.78 (0.70–0.87)
    <20 y1.23 (1.10–1.37)1.65 (1.27–2.15)
Maternal educationa
    High1.001.00
    Medium high1.16 (1.10–1.22)1.20 (1.03–1.40)
    Medium low1.24 (1.18–1.31)1.23 (1.05–1.42)
    Low1.39 (1.32–1.46)1.44 (1.24–1.66)
Maternal smoking during pregnancy
    No1.001.00
    Yes1.03 (0.97–1.09)1.47 (1.27–1.69)
Breastfeeding initiation at hospital
    Yes1.001.00
    No1.19 (1.12–1.26)1.33 (1.14–1.54)
First Nations status
    No1.001.00
    Yes1.65 (1.46–1.86)2.94 (2.31–3.75)
Parity (older siblings)
    No1.001.00
    Yes1.58 (1.53–1.65)2.24 (2.01–2.51)
Birth weight
    2500–4000 g (normal)1.001.00
    ≥4000 g (high)0.89 (0.84–0.93)0.80 (0.68–0.93)
    1500–2500 g (low)1.29 (1.18–1.42)2.64 (2.19–3.18)
    <1500 g (very low)1.84 (1.50–2.25)6.19 (4.53–8.48)
Congenital anomalies
    No1.001.00
    Yes1.18 (0.98–1.41)2.16 (1.49–3.14)
  • Analyses were performed with Cox's proportional-hazards model.

  • a High was defined as >44% of neighborhood residents with postsecondary education, medium high as 36% to 44%, medium low as 28% to 36%, and low as <28%; infants were assigned to categories on the basis of mothers' postal codes of residence.