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Table 4 Relative risks estimates (hazard ratios) according to prenatal, neonatal/perinatal and postnatal/environmental conditions for hospitalization

From: Risk factors for bronchiolitis hospitalization during the first year of life in a multicenter Italian birth cohort

Exposures Bronchiolitis hospitalization +/- exposed (%) Multivariable HRa (95%b)
  Events/unexposed Events/exoposed [HRc, 95 % CI]  
Gender-male 44/1060 (4.2) 76/1150 (6.6) [1.6, 1.1-2.3] 1.6 (1.1-2.4)
Week of gestational age    
33-34 vs > 37 25/706 (3.5) 54/737 (7.3) [2.1, 1.3-3.4]  
35-37 vs > 37 25/706 (3.5) 41/767 (5.3) [1.5, 0.9-2.5]  
Prenatal    
Mother’s history of BPCO 117/2184 (5.4) 3/26 (11.5) [2.2, 0.7–6.9]  
Mother’s history of eczema 113/2123 (5.3) 7/87 (8.0) [1.6, 0.7–3.4]  
Father’s history of BPCO 115/2180 (5.3) 5/30 (16.7) [3.6, 1.5–8.9]  
Assisted reproductive technology 115/1959 (5.9) 5/251 (2.0) [0.3, 0.1–0.6]  
Treatment with corticosteroids 75/1645 (4.6) 45/565 (8.0) [1.4, 0.9–2.2] 1.6 (1.1–2.4)
Mother’s pregnancy pathologies 78/1623 (4.8) 42/587 (7.2) [1.4, 0.9–2.0]  
Prenatal smoke exposure 58/1358 (4.3) 62/852 (7.3) [1.8, 1.2–2.5] 1.6 (1.1–2.3)
Neonatal/Perinatal    
Delivery    
Singleton 23/537 (4.3) 97/1673 (5.8) [1.9, 1.2–3.0] 1.8 (1.1–2.9)
Resuscitation with O2 95/1911 (5.0) 25/299 (8.4) [1.4, 0.9–2.3)]  
Perinatal    
Neonatal hospitalization 83/1770 (4.7) 37/440 (8.4) [1.5, 1.0–2.2] 1.6 (1.0–2.5)
Surfactant therapy 109/2150 (5.1) 11/60 (18.3) [3.8, 1.6–5.8] 2.0 (1.1–3.8)
Postnatal (environmental)    
Having siblings < 10 years 40/1310 (3.1) 73/792 (9.2) [3.3, 2.2–4.8] 3.0 (2.0–4.5)
       ≥ 10 years 40/1310 (3.1) 7/108 (6.5) [2.2, 1.0–5.0] 1.9 (0.9–4.4)
Environmental (home) conditions    
Residential crowding 93/1983 (4.7) 27/227 (11.9) [2.6, 1.7–3.9] 2.4 (1.5–3.7)
Indoor humidity 101/1988 (5.1) 19/222 (8.6) [1.7, 1.0–2.8] 1.6 (1.0–2.6)
Heating system generating smoke 90/1742 (5.2) 30/468 (6.4) [1.2, 0.8–1.8]  
Residence in the proximity of intense vehicular traffic roads 100/1926 (5.2) 20/284 (7.0) [1.4, 0.9–2.3]  
Sibilings 63/1414 (4.5) 57/796 (7.2) [1.6, 1.1–2.3]  
Lack of breastfeeding 78/1728 (4.5) 42/482 (8.7) [1.8, 1.2-2.6] 1.8 (1.2-2.6)
Passive cigarette smoke exposure 112/2102 (5.3) 8/108 (7.4) [1.5, 0.7–3.1]  
Exposed to epidemic RSV season 31/887 (3.5) 89/1323 (6.7) [2.0, 1.3–3.0] 1.9 (1.3–2.9)
  1. aEstimates from a model including all significant variables at gender and weeks of gestational age adjusted analysis
  2. b95 % Confidence Interval
  3. cHazard ratios estimates adjusted for gender and weeks of gestational age