Table 1.
Characteristics of study sample and eligible ALSPAC participants.
| Study sample | ||||||||
|---|---|---|---|---|---|---|---|---|
| Characteristic | Boys (n = 3,664) | Girls (n = 3,412) | Total (n = 7,076) | ALSPACa (n = 12,931) | ||||
| PSAI score (mean ± SD) | 62.3 ± 8.6 | 36.9 ± 9.3 | 50.1 ± 15.5 | 50.0 ± 15.6 | ||||
| Missing (n) | — | — | — | 3,580 | ||||
| Age at PSAI completion [months (mean ± SD)] | 42.3 ± 0.8 | 42.3 ± 0.8 | 42.3 ± 0.8 | 42.3 ± 0.9 | ||||
| Missing (n) | 80 | 83 | 163 | 3,809 | ||||
| Maternal age [years (mean ± SD)] | 28.9 ± 4.7 | 28.6 ± 4.6 | 28.7 ± 4.7 | 28.0 ± 5.0 | ||||
| Missing (n) | 0 | 0 | 0 | 0 | ||||
| Mother interaction score (mean ± SD) | 28.5 ± 4.9 | 28.8 ± 4.7 | 28.6 ± 4.8 | 28.6 ± 4.8 | ||||
| Missing (n) | 8 | 3 | 11 | 3,597 | ||||
| Partner interaction score (mean ± SD) | 20.4 ± 7.9 | 20.1 ± 8.1 | 20.3 ± 8.0 | 20.1 ± 8.1 | ||||
| Missing (n) | 15 | 22 | 37 | 3,638 | ||||
| Partner absent [n (%)] | 216 (5.9) | 219 (6.5) | 435 (6.1) | 609 (6.6) | ||||
| Infant feeding method [n (%)] | ||||||||
| Early formula | 2,697 (73.6) | 2,488 (72.9) | 5,185 (73.3) | 6,294 (73.9) | ||||
| Early soy | 89 (2.4) | 68 (2.0) | 157 (2.2) | 182 (2.1) | ||||
| Late soy | 167 (4.6) | 139 (4.1) | 306 (4.3) | 359 (4.2) | ||||
| Primarily breast-fed | 711 (19.4) | 717 (21.0) | 1,428 (20.2) | 1,684 (19.8) | ||||
| Missing (n) | — | — | — | 4,412 | ||||
| Presence of older brother [n (%)] | ||||||||
| No | 2,344 (66.6) | 2,261 (69.1) | 4,605 (67.8) | 6,816 (66.4) | ||||
| Yes (≥ 1) | 1,175 (33.4) | 1,010 (30.9) | 2,185 (32.2) | 3,443 (33.6) | ||||
| Missing (n) | 145 | 141 | 286 | 2,672 | ||||
| Presence of older sister [n (%)] | ||||||||
| No | 2,399 (68.2) | 2,294 (70.2) | 4,693 (69.2) | 6,991 (68.2) | ||||
| Yes (≥ 1) | 1,118 (31.8) | 976 (29.8) | 2,094 (30.8) | 3,264 (31.8) | ||||
| Missing (n) | 147 | 142 | 289 | 2,676 | ||||
| Regular child care attendance [n (%)] | ||||||||
| No | 2,229 (64.3) | 2,017 (62.3) | 4,246 (63.3) | 5,943 (63.0) | ||||
| Yes | 1,240 (35.7) | 1,223 (37.7) | 2,463 (36.7) | 3,490 (37.0) | ||||
| Missing (n) | 195 | 172 | 367 | 3,498 | ||||
| Prenatal smoking [n (%)] | ||||||||
| No | 2,924 (82.7) | 2,769 (83.7) | 5,693 (83.2) | 8,898 (80.5) | ||||
| Yes | 611 (17.3) | 539 (16.3) | 1,150 (16.8) | 2,162 (19.5) | ||||
| Missing (n) | 129 | 104 | 233 | 1,871 | ||||
| Maternal education [n (%)] | ||||||||
| University degree | 505 (14.7) | 498 (15.6) | 1,003 (15.1) | 1,497 (13.8) | ||||
| Advanced level | 865 (25.2) | 826 (25.8) | 1,691 (25.5) | 2,607 (24.1) | ||||
| Ordinary level | 1,316 (38.4) | 1,195 (37.4) | 2,511 (37.9) | 4,002 (36.9) | ||||
| Vocational | 337 (9.8) | 297 (9.3) | 634 (9.6) | 1,132 (10.5) | ||||
| CSE/none | 406 (11.8) | 379 (11.9) | 785 (11.9) | 1,596 (14.7) | ||||
| Missing (n) | 235 | 217 | 452 | 2,097 | ||||
| aEligible ALSPAC participants are limited to term, singleton infants alive at 1 year. | ||||||||