TABLE 2.
Demographic data and subjects’ characteristics at baseline in the study groups
| Active group, N = 388 | Control group, N = 379 | P | ||
| Sex* | ||||
| Female | 175 (45.1) | 157 (41.4) | 0.304 | |
| Male | 213 (54.9) | 222 (58.6) | ||
| Age at screening, mo† | 19 (14–24) | 19 (15–24) | 0.283 | |
| Ethnicity* | ||||
| Asian | 165 (42.5) | 159 (42.0) | 0.658 | |
| Black | 4 (1.0) | 6 (1.6) | ||
| White | 202 (52.1) | 189 (49.9) | ||
| Combination | 16 (4.1) | 23 (6.1) | ||
| Other | 1 (0.3) | 2 (0.5) | ||
| Season of birth* | ||||
| Autumn | 95 (24.5) | 87 (23.0) | 0.874 | |
| Spring | 88 (22.7) | 94 (24.8) | ||
| Summer | 70 (18.0) | 71 (18.7) | ||
| Winter | 135 (34.8) | 127 (33.5) | ||
| Type of delivery* | ||||
| Caesarean | 109 (28.1) | 106 (28.0) | 0.969 | |
| Vaginal | 279 (71.9) | 273 (72.0) | ||
| Gestational age, wk† | 39 (38–40) | 39 (38–40) | 0.890 | |
| Length at birth, cm† | 50 (48–53) | 51 (49–53) | 0.241 | |
| Weight at birth, kg† | 3 (3–4) | 3 (3–4) | 0.546 | |
| Estimated total number of infection episodes in the last 6 mo‡ | 3.4 (2.17) | 3.4 (2.17) | 0.942 | |
| Start age of breast-feeding, mo† | 0 (0–0) | 0 (0–0) | 0.606 | |
| End age of breast-feeding, mo† | 5 (2–9) | 5 (3–9) | 0.230 | |
| Start age of formula feeding, mo† | 3 (1–6) | 4 (1–6) | 0.381 | |
| End age of formula feeding, mo† | 18 (14–23) | 18 (14–23) | 0.955 | |
| Start age of cow's milk, mo† | 12 (12–15) | 12 (12–13) | 0.972 | |
| End age of cow's milk† | 30 (27–37) | 33 (29–38) | 0.082 | |
| Start age of weaning food, mo† | 6 (4–6) | 6 (4–6) | 0.426 | |
| Living area of the family* | ||||
| Rural | 37 (9.5) | 36 (9.5) | 0.897 | |
| Suburban | 136 (35.1) | 127 (33.5) | ||
| Urban | 215 (55.4) | 216 (57.0) | ||
| No. rooms in the family house (excl. kitchens, bathrooms, and toilets)* | ||||
| 1–3 | 183 (47.8) | 192 (51.3) | 0.345 | |
| 4–6 | 190 (49.6) | 168 (44.9) | ||
| >6 | 10 (2.6) | 14 (3.7) | ||
| Missing | 5 | 5 | ||
| No. people living at the family house (excl. participating child)* | ||||
| 0 | 0 (0.0) | 1 (0.3) | ||
| 1–3 | 225 (58.7) | 236 (63.1) | 0.410 | |
| 4–6 | 138 (36.0) | 117 (31.3) | ||
| >6 | 20 (5.2) | 20 (5.3) | ||
| Missing | 5 | 5 | ||
| No. siblings of the child (excl. participating child)* | ||||
| 0 | 136 (35.2) | 162 (42.7) | 0.571 | |
| 1 | 166 (43.0) | 145 (38.3) | ||
| 2 | 55 (14.2) | 45 (11.9) | ||
| 3 | 21 (5.4) | 20 (5.3) | ||
| 4 | 4 (1.0) | 3 (0.8) | ||
| 5 | 3 (0.8) | 3 (0.8) | ||
| >5 | 1 (0.3) | 1 (0.3) | ||
| Missing | 2 | 0 | ||
| Smoking during pregnancy of child* | ||||
| No | 364 (95.3) | 358 (95.2) | 0.961 | |
| Yes | 18 (4.7) | 18 (4.8) | ||
| Missing | 6 | 3 | ||
| Age of father, y† | 33 (30–37) | 33 (30–37) | 0.868 | |
| Age of mother, y† | 31 (27–34) | 31 (27–34) | 0.466 | |
| Age of siblings, y† | 5 (2–8) | 4 (2–7) | 0.328 | |
*N (%), P from the χ2 test.
†Median (Q1–Q3), P from the Wilcoxon rank-sum test.