Characteristics of study population, by duration of breastfeeding (N=151)
| Breastfeeding categories | |||||
|---|---|---|---|---|---|
| Total (N=111) | Never (N=24) | ≤3 months (N=37) | >3 months (N=50) | p Value* | |
| Age† (years) | 14.1 (2.5) | 14.7 (2.7) | 14.3 (2.9) | 13.5 (2.0) | 0.111 |
| Height† (cm) | 160.8 (10.9) | 164.0 (13.5) | 158.7 (10.8) | 160.9 (9.4) | 0.190 |
| Weight† (kg) | 53.8 (13.1) | 58.2 (17.2) | 52.8 (13.1) | 52.5 (10.5) | 0.189 |
| Gestational age† (weeks) | 38.5 (2.3) | 39.0 (1.9) | 38.4 (2.5) | 38.9 (2.0) | 0.371 |
| Birth weight (g) | 3235.8 (599.2) | 3111.2 (622.2) | 3212.7 (605.1) | 3313.8 (583.9) | 0.386 |
| Sex‡ | |||||
| Male | 51 (46.0) | 23 (63.9) | 14 (32.6) | 35 (48.1) | 0.021 |
| Female | 60 (54.0) | 13 (36.1) | 29 (67.4) | 37 (51.4) | |
| Ethnicity‡ | |||||
| South-Asian | 24 (21.6) | 5 (20.8) | 9 (37.5) | 10 (41.7) | 0.884 |
| White | 87 (78.4) | 19 (21.8) | 28 (32.2) | 40 (45.9) | |
| Smoking during pregnancy‡ | |||||
| No | 100 (90.1) | 18 (18.0) | 36 (36.0) | 46 (46.0) | 0.014 |
| Yes | 11 (9.9) | 6 (54.5) | 1 (9.1) | 4 (36.4) | |
| Early-onset wheeze‡ | |||||
| No | 88 (79.3) | 19 (21.6) | 31 (35.2) | 38 (43.2) | 0.676 |
| Yes | 23 (20.7) | 5 (21.7) | 6 (26.1) | 12 (52.2) | |
| Maternal asthma‡ | |||||
| No | 88 (79.3) | 15 (17.05) | 31 (35.23) | 42 (47.73) | 0.052 |
| Yes | 22 (19.8) | 9 (40.91) | 6 (27.27) | 7 (31.82) | |
| Missing | 1 (0.9) | 0 (0.0) | 0 (0.0) | 1 (100.0) | |
| FVC§ (L) | 3.5 (0.7) | 3.76 (0.92) | 3.41 (0.74) | 3.53 (0.63) | 0.183 |
| FEV1§ (L) | 3.0 (0.6) | 3.23 (0.75) | 2.94 (0.62) | 3.04 (0.52) | 0.197 |
| FEF50§ (L/s) | 3.6 (0.6) | 3.78 (0.74) | 3.50 (0.62) | 3.61 (0.53) | 0.220 |
| FRC§ (L) | 2.2 (0.5) | 2.37 (0.59) | 2.17 (0.51) | 2.19 (0.40) | 0.227 |
| RV§ (L) | 1.2 (0.2) | 1.31 (0.29) | 1.22 (0.25) | 1.22 (0.19) | 0.233 |
| TLC§ (L) | 4.7 (0.9) | 4.94 (1.15) | 4.50 (0.94) | 4.64 (0.78) | 0.196 |
| ADC¶ (cm2/s) | 0.096 (0.012) | 0.095 (0.012) | 0.096 (0.012) | 0.095 (0.013) | 0.444 |
*The p value is based on a χ2 test.
†Mean (SD).
‡N (%); the percentages represent breastfeeding frequencies within levels of confounder (row percentages).
§The means of the outcome variables are predicted values adjusted for age, sex, height, weight using linear regression.
¶The ADC analysis was performed using the natural logarithm, adjusting for age, sex, height and ln FRC; the estimates were back-transformed from the logarithmic scale to the original scale, therefore the estimated means are geometric means.
ADC, apparent diffusion coefficient; ETS, exposure to tobacco smoke; FEF50, forced mid-expiratory flow; FEV1, forced expiratory volume at 1 s; FRC, functional residual capacity; FVC, forced vital capacity; RV, residual volume; TLC, total lung capacity; VC, vital capacity.