Table 1 Demographic and clinical characteristics. Infants with LRTI were defined as those who developed bronchiolitis, bronchitis, or pneumonia during the first year of life as defined by ICD9 or ICD10 diagnosis in the Boston Birth Cohort (BBC) database. Maternal age, body mass index (BMI), and infant gestational age (GA) at birth are displayed as median and IQR (interquartile range) as their distributions were not Gaussian. There were significant differences in sex, parity, number of preterm infants, type of delivery, maternal smoking, and breastfeeding status between the two groups. There were also significant differences in maternal BMI and infant gestational age at birth between the group of infants who developed LRTI during the first year of life compared with those that did not. There were none or minimal amounts of missing data (< 1%) in most covariates, except for breastfeeding status that was unknown in ~ 11% of children.
Variable | All infants (n = 2,790) | Infants with LRTI (n = 375) | Infants without LRTI (n = 2,415) | p-value |
|---|---|---|---|---|
Sex (n, %) | 0.003 | |||
Female | 1,377 (49.4) | 158 (42.1) | 1,219 (50.5) | |
Male | 1,413 (50.7) | 217 (57.9) | 1,196 (49.5) | |
Maternal race (n, %) | 0.234 | |||
White | 205 (7.4) | 27 (7.2) | 178 (7.4) | |
Black | 1644 (58.9) | 206 (54.9) | 1438 (59.5) | |
Hispanic | 619 (22.2) | 77 (23.2) | 532 (22.0) | |
Asian/Pacific Islander | 44 (1.6) | 6 (1.6) | 38 (1.6) | |
Other/mixed race | 278 (10.0) | 49 (13.1) | 229 (9.5) | |
Maternal age in years | 0.797 | |||
Median (IQR) | 28.3 (23.5–33.4) | 28.2 (22.6–33.8) | 28.3 (23.6–33.4) | |
Maternal Education* (n, %) | 0.710 | |||
No school/Elementary | 116 (4.1) | 16 (4.3) | 100 (4.1) | |
Some secondary school | 622 (22.7) | 94 (27.1) | 528 (21.9) | |
High school graduate/GED | 1014 (36.3) | 136 (36.3) | 878 (36.4) | |
Some college | 626 (22.4) | 79 (21.1) | 547 (22.7) | |
College degree and above | 395 (14.2) | 47 (12.5) | 348 (14.4) | |
Unknown | 17 (0.6) | 3 (0.8) | 14 (0.6) | |
Multiparous mother (n, %) | 1626 (58.3) | 242 (64.5) | 1384 (57.3) | 0.008 |
Body Mass Index (BMI) | 0.006 | |||
Median (IQR) | 25.6 (22.4–30.0) | 26.6 (22.9–31.2) | 25.5 (22.3–29.8) | |
BMI category (n, %) | 0.011 | |||
Normal | 1294 (46.4) | 148 (39.5) | 1146 (47.5) | |
Overweight (BMI 25–29.9) | 808 (29.0) | 117 (31.2) | 691 (28.6) | |
Obese (BMI ≥ 30) | 688 (24.7) | 110 (29.3) | 578 (23.9) | |
Gestational Age (weeks) (n, %) | 38.7 (36.6–40.0) | 38.1 (35.0–39.4) | 38.9 (36.7–40.1) | 0.000 |
Prematurity (< 37 wks.) (n,%) | 789 (28.3) | 141 (37.6) | 648 (26.8) | 0.000 |
Type of Delivery* | 0.002 | |||
Vaginal Delivery | 1,761 (63.1) | 210 (56.0) | 1551 (64.2) | |
C-section | 1017 (36.5) | 165 (44.0) | 852 (35.3) | |
Unknown | 12 (0.4) | 0 | 12 (0.5) | |
Maternal diabetes (n,%) | 352(12.6) | 294(12.2) | 58(15.5) | 0.074 |
Gestational Diabetes | 222 (8.0) | 34 (9.1) | 188 (7.8) | |
Type 1 or 2 Diabetes | 130 (4.7) | 24 (6.4) | 106 (4.4) | |
Hypertensive disorders of pregnancy* (n, %) | 430 (15.4) | 352 (14.6) | 78 (20.8) | 0.003 |
Preeclampsia, Eclampsia, HELLP syndrome | 241 (8.6) | 45 (12.0) | 196 (8.1) | |
Chronic Hypertension | 189 (6.8) | 33 (8.8) | 156 (6.5) | |
Unknown status | 20 (0.7) | 0 | 20 (0.8) | |
Pregnancy smoking* (n, %) | 0.048 | |||
Continuous smoking | 307 (11.0) | 54 (14.4) | 253 (10.5) | |
Unknown status | 19 (0.7) | 1 (0.3) | 18 (0.8) | |
Breastfeeding status* (n, %) | 0.010 | |||
Breastfed infant (exclusive/partial) | 1831 (65.6) | 232 (61.9) | 1599 (66.2) | |
Unknown status | 298 (10.7) | 32 (8.5) | 266 (11.1) |
