Table 1 Characteristics of study population
Number (%) or Mean ± SD | at 24 months | |||||
|---|---|---|---|---|---|---|
P | MDI | PDI | ||||
Mean ± SD | P | Mean ± SD | P | |||
Total | 720 | 97.01 ± 14.52 | 96.78 ± 13.50 | |||
Maternal characteristics | ||||||
Maternal age, years | ||||||
≤30 | 429 (59.6) | <0.001 | 98.28 ± 14.45 | 0.004 | 97.00 ± 13.57 | 0.59 |
>30 | 291 (40.4) | 95.13 ± 14.44 | 96.45 ± 13.42 | |||
Maternal education | ||||||
≤High school | 284 (39.4) | <0.001 | 95.23 ± 14.60 | 0.03 | 94.64 ± 13.74 | 0.002 |
≥University | 372 (51.7) | 98.16 ± 14.40 | 98.04 ± 13.31 | |||
missing | 64 (8.9) | 98.25 ± 14.27 | 98.97 ± 12.42 | |||
Region | ||||||
Seoul | 177 (24.6) | <0.001 | 95.51 ± 14.43 | 0.02 | 97.97 ± 13.03 | <0.001 |
Cheonan | 340 (47.2) | 96.34 ± 15.20 | 93.53 ± 12.84 | |||
Ulsan | 203 (28.2) | 99.44 ± 13.14 | 101.19 ± 13.63 | |||
GSTM1 | ||||||
Present (=positive) | 315 (44.4) | 0.003 | 96.19 ± 14.10 | 0.22 | 95.88 ± 12.66 | 0.12 |
Null (=negative) | 394 (55.6) | 97.53 ± 14.92 | 97.47 ± 14.20 | |||
GSTT1 | ||||||
Present (=positive) | 345 (48.7) | 0.48 | 96.32 ± 14.50 | 0.28 | 96.30 ± 13.25 | 0.38 |
Null (=negative) | 364 (51.3) | 97.51 ± 14.62 | 97.20 ± 13.84 | |||
Urinary cotinine | ||||||
≤mediana | 368 (50.6) | 0.74 | 97.05 ± 14.81 | 0.80 | 96.86 ± 14.07 | 0.80 |
>mediana | 359 (49.4) | 96.77 ± 14.43 | 96.60 ± 12.97 | |||
Infant characteristics | ||||||
Infant sex | ||||||
Male | 381 (52.9) | 0.12 | 92.56 ± 14.31 | <0.001 | 94.81 ± 13.45 | <0.001 |
Female | 339 (47.1) | 102.01 ± 13.07 | 99.00 ± 13.23 | |||
Breastfeeding only up to 6 months | ||||||
Yes | 257 (35.7) | <0.001 | 98.81 ± 14.40 | 0.04 | 97.33 ± 14.30 | 0.11 |
No | 383 (59.2) | 95.87 ± 14.55 | 95.93 ± 13.04 | |||
missing | 80 (11.1) | 96.68 ± 14.37 | 99.11 ± 12.81 | |||
Primary caregiver during the first 24 months after birth | ||||||
Mother | 368 (51.1) | 0.55 | 97.90 ± 14.42 | 0.09 | 96.49 ± 13.99 | 0.56 |
Others | 352 (48.9) | 96.08 ± 14.58 | 97.09 ± 12.98 | |||
Gestational Age | 39.06 ± 1.08 | |||||