Table 1.
Characteristics of all school beginners within the study region (population), children included in the analysis sample, and children of the analysis sample belonging to the quarter with the youngest age at school entrya
| Characteristics | Population N = 3683 |
Analysis sample N = 1633 |
Youngest quarter of analysis sample N = 430 |
|---|---|---|---|
| Child | |||
| Male, n (%) | 1909 (51.9) | 843 (51.6) | 206 (47.9) |
| Missing, n | 7 | 0 | 0 |
| Migrant background, n (%) | 822 (25.5) | 325 (20.9) | 91 (22.0) |
| Missing, n | 464 | 80 | 17 |
| Age at PHE, M (SD) | 5.9 (0.4) | 5.9 (0.3) | 5.5 (0.2) |
| Missing, n | 1 | 0 | 0 |
| Family | |||
| Family structure: nuclear family, n (%) | 2855 (86.0) | 1385 (86.9) | 380 (90.0) |
| Missing, n | 363 | 40 | 8 |
| Multiples, n (%) | 105 (2.9) | 53 (3.3) | 13 (3.0) |
| Missing, n | 36 | 15 | 3 |
| Abitur/Fachhochschulreife (A-level exams) Mother, n (%) | 1825 (60.4) | 941 (63.5) | 255 (63.6) |
| Missing, n | 662 | 150 | 29 |
| Abitur/Fachhochschulreife (A-level exams) Father, n (%) | 1768 (61.0) | 874 (61.1) | 236 (61.5) |
| Missing, n | 784 | 203 | 46 |
| Smoking in household | |||
| Never, n (%) | 3033 (91.9) | 1455 (91.7) | 374 (90.6) |
| Seldom, n (%) | 191 (5.8) | 96 (6.0) | 28 (6.8) |
| Often, n (%) | 77 (2.3) | 36 (2.3) | 11 (2.7) |
| Missing, n | 382 | 46 | 17 |
| Breastfeeding | |||
| Not at all, n (%) | 573 (17.5) | 264 (16.8) | 62 (15.1) |
| Up to 6 months, n (%) | 1312 (40.2) | 630 (40.2) | 181 (44.1) |
| More than 6 months, n (%) | 1382 (42.3) | 674 (43.0) | 167 (40.7) |
| Missing, n | 416 | 65 | 20 |
PHE Preschool health examination, M Mean, SD Standard deviation
Percentages relate to non-missing values
aAge at school entry 6.0–6.25 years