TABLE 1

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

VariableOutpatient or Inpatient Bronchiolitis Case DefinitionInpatient Bronchiolitis Case Definition
n (%)Unadjusted Hazard Rate Ratio (95% Confidence Interval)n (%)Unadjusted Hazard Rate Ratio (95% Confidence Interval)
BronchiolitisNo BronchiolitisBronchiolitisNo Bronchiolitis
Gender
    Female5150 (41.3)40 028 (49.7)1.00628 (39.5)44 550 (48.7)1.00
    Male7324 (58.7)40 524 (50.3)1.37 (1.32–1.42)960 (60.5)46 888 (51.3)1.46 (1.32–1.62)
Maternal age
    20–29 y4580 (36.7)26 343 (32.7)1.00586 (36.9)30 337 (33.2)1.00
    >29 y7524 (60.3)52 335 (65.0)0.84 (0.81–0.87)935 (58.9)58 924 (64.4)0.82 (0.74–0.91)
    <20 y370 (3.0)1874 (2.3)1.12 (1.01–1.25)67 (4.2)2177 (2.4)1.58 (1.23–2.04)
Maternal educationa
    High2531 (20.3)21 051 (26.1)1.00300 (18.9)23 282 (25.5)1.00
    Medium high3056 (24.5)20 716 (25.7)1.21 (1.15–1.28)377 (23.7)23 395 (25.6)1.25 (1.08–1.46)
    Medium low3286 (26.3)20 092 (24.9)1.34 (1.27–1.41)415 (26.1)22 963 (25.1)1.41 (1.22–1.64)
    Low3601 (28.9)18 693 (23.2)1.56 (1.48–1.64)496 (31.2)21 798 (23.8)1.78 (1.55–2.06)
Maternal smoking during pregnancy
    No11 217 (89.9)73 432 (91.2)1.001351 (85.1)83 298 (91.1)1.00
    Yes1257 (10.1)7120 (8.8)1.14 (1.08–1.21)237 (14.9)8140 (8.9)1.78 (1.55–2.04)
Breastfeeding initiation at hospital
    Yes11 267 (90.3)74 788 (92.8)1.001383 (87.1)84 672 (92.6)1.00
    No1207 (9.7)5764 (7.2)1.36 (1.28–1.44)205 (12.9)6766 (7.4)1.86 (1.61–2.16)
First Nations status
    No12 210 (97.9)79 738 (99.0)1.001516 (95.5)90 432 (98.9)1.00
    Yes264 (2.1)814 (1.0)1.98 (1.76–2.24)72 (4.5)1006 (1.1)4.23 (3.34–5.35)
Parity (siblings)
    No4560 (36.6)38 162 (47.4)1.00474 (29.9)42 248 (46.2)1.00
    Yes7914 (63.4)42 390 (52.6)1.52 (1.47–1.58)1114 (70.1)49 190 (53.8)2.04 (1.83–2.04)
Birth weight
    2500–4000 g10 222 (81.9)66 380 (82.4)1.001239 (78.0)75 363 (82.4)1.00
    ≥4000 g1666 (13.4)11 371 (14.1)0.95 (0.90–1.01)185 (11.7)12 852 (14.1)0.88 (0.75–1.02)
    1500–2500 g489 (3.9)2492 (3.1)1.25 (1.14–1.37)122 (7.7)2859 (3.1)2.56 (2.12–3.08)
    <1500 g97 (0.8)309 (0.4)1.88 (1.54–2.29)42 (2.6)364 (0.4)6.56 (4.82–8.92)
Congenital anomalies
    No12 355 (99.0)79 932 (99.2)1.001560 (98.2)90 727 (99.2)1.00
    Yes119 (1.0)620 (0.8)1.22 (1.02–1.46)28 (1.8)711 (0.8)2.26 (1.56–3.29)
Household incomeb
    High1635 (13.1)13 272 (16.5)1.00207 (13.0)14 700 (16.1)1.00
    Medium high2246 (18.0)15 485 (19.2)1.17 (1.09–1.24)295 (18.6)17 436 (19.1)1.20 (1.01–1.44)
    Medium2643 (21.2)16 945 (21.0)1.25 (1.17–1.33)320 (20.2)19 268 (21.1)1.19 (1.00–1.41)
    Medium low2930 (23.5)17 490 (21.7)1.33 (1.26–1.42)378 (23.8)20 042 (21.8)1.35 (1.14–1.60)
    Low3020 (24.2)17 360 (21.6)1.38 (1.30–1.47)388 (24.4)19 992 (21.9)1.39 (1.17–1.64)
Residencec
    Urban11 148 (89.3)71 061 (88.2)1.001374 (86.5)80 805 (88.4)1.00
    Small town120 (1.0)841 (1.0)0.91 (0.76–1.09)21 (1.3)940 (1.0)1.30 (0.84–1.99)
    Rural fringe955 (7.7)7040 (8.7)0.87 (0.82–0.93)155 (9.8)7839 (8.6)1.15 (0.98–1.36)
    Rural261 (2.1)1632 (2.0)1.02 (0.90–1.15)38 (2.4)1854 (2.0)1.20 (0.87–1.66)
Gestational aged
    >35 wk11 949 (95.8)78 369 (97.3)1.001432 (90.2)88 886 (97.2)1.00
    33–35 wk346 (2.8)1603 (2.0)1.37 (1.23–1.53)87 (5.5)1862 (2.0)2.85 (2.30–3.54)
    29–32 wk121 (1.0)436 (0.5)1.70 (1.42–2.04)44 (2.8)513 (0.6)5.08 (3.77–6.86)
    25–28 wk58 (0.5)144 (0.2)2.33 (1.80–3.01)25 (1.6)177 (0.2)8.04 (5.42–11.9)
Preterm complications
    No11 457 (91.8)74 995 (93.1)1.001378 (86.8)85 074 (93.0)1.00
    Yes1017 (8.2)5557 (6.9)1.18 (1.11–1.26)210 (13.2)6364 (7.0)2.02 (1.75–2.34)
Low birth weight complications
    No11 504 (92.2)75 273 (93.4)1.001386 (87.3)85 391 (93.4)1.00
    Yes970 (7.8)5279 (6.6)1.19 (1.12–1.27)202 (12.7)6047 (6.6)2.04 (1.76–2.37)
  • 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.

  • b The distribution of median household incomes within a neighborhood according to quintile was determined; infants were assigned to categories on the basis of mothers' postal codes of residence.

  • c Categories were based on Census population density data, with urban defined as an area with >400 people per km2.

  • d Categories were based on American Academy of Pediatrics guidelines.52