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Table 2 Characteristics of infants and their biological mothers (N = 374)

From: β2-Adrenergic receptor promoter haplotype influences the severity of acute viral respiratory tract infection during infancy: a prospective cohort study

  Caucasian (N = 261) African American (N = 113) P value
Infant characteristics
Birth weight (grams) (N = 372), median (IQR*) 3345 (3090, 3657) 3147 (2892, 3430) <0.001
Gestational age (weeks) (N = 371), median (IQR) 39 (38,40) 39 (38,40) 0.498
Male gender, n (%) 140 (54) 67 (59) 0.313
Age at enrollment (weeks), median (IQR) 10 (6, 21) 18 (7, 35) <0.001
Breastfeeding, n (%) 152 (58) 46 (41) 0.002
Daycare attendance, n (%) 68 (26) 39 (35) 0.096
Secondhand smoke exposure (N = 371), n (%) 158 (61) 64 (57) 0.486
Having siblings, n (%) 198 (76) 85 (75) 0.894
Insurance type, n (%)
 Private 111 (43) 9 (8) <0.001
 Medicare 135 (52) 101 (89)  
 None 15 (6) 3 (3)  
Season of enrollment, n (%)
 2004 – 2005 42 (16) 21 (19) 0.590
 2005 – 2006 76 (29) 38 (34)  
 2006 – 2007 75 (29) 31 (27)  
 2007 – 2008 68 (26) 23 (20)  
RSV positive 180 (69) 59 (52) 0.002
Lower respiratory tract infection vs. upper respiratory infection, n (%) 213 (82) 72 (64) <0.001
Bronchiolitis severity score (n = 373), median (IQR) 6.5 (3, 9) 4 (1, 7) <0.001
Maternal characteristics
Maternal age at enrollment (years) 27 (22, 31) 24 (21, 27) <0.001
Maternal education, years (n = 313), n (%)
 <12 42 (19) 16 (17) 0.004
 12 56 (25) 41 (44)  
 >12 122 (55) 36 (39)  
Maternal asthma, n (%) 50 (19) 27 (24) 0.298
  1. Abbreviations: IQR interquartile range