| Observations of children from 2-child families (n) | 5388 | 1920 | 1201 | 1095 | 1172 |
| Number of peers per child (mean, SD) | 40.7 (22.9) | 36.4 (22.6) | 42.4 (25.6) | 41.0 (19.6) | 45.7 (22.3) |
| Age (mean, SD) | 8.4 (3.2) | 5.1 (1.3) | 7.9 (0.6) | 9.9 (0.6) | 13.1 (1.4) |
| Sex (n, %) |
| Boys | 2795 (51.9) | 1041 (54.2) | 609 (50.7) | 557 (50.9) | 588 (50.2) |
| Girls | 2593 (48.1) | 879 (45.8) | 592 (49.3) | 538 (49.1) | 584 (49.8) |
| Parental education level (n, %)2 |
| Low or medium education | 2481 (46.1) | 861 (44.8) | 546 (45.5) | 493 (45.0) | 581 (49.6) |
| High education | 2907 (53.9) | 1059 (55.2) | 655 (54.5) | 602 (55.0) | 591 (50.4) |
| Country (n, %) |
| Italy | 1084 (20.1) | 350 (18.2) | 247 (20.6) | 229 (20.9) | 258 (22.0) |
| Estonia | 428 (7.9) | 156 (8.1) | 68 (5.7) | 127 (11.6) | 77 (6.6) |
| Cyprus | 724 (13.4) | 132 (6.9) | 120 (10.6) | 145 (13.2) | 327 (27.9) |
| Belgium | 476 (8.8) | 231 (12.0) | 134 (11.2) | 74 (6.8) | 37 (3.2) |
| Sweden | 908 (16.9) | 426 (22.2) | 234 (19.5) | 154 (14.1) | 94 (8.0) |
| Germany | 684 (12.7) | 232 (12.1) | 152 (12.7) | 124 (11.3) | 176 (15.0) |
| Hungary | 528 (9.8) | 146 (7.6) | 111 (9.2) | 121 (11.1) | 150 (12.8) |
| Spain | 556 (10.3) | 247 (12.9) | 135 (11.2) | 121 (11.1) | 53 (4.5) |
| Children’s lifestyle behavior |
| Fast food consumption (frequency/week) | 1.02 (1.66) | 0.44 (0.67) | 0.47 (0.68) | 0.62 (1.00) | 2.92 (2.43) |
| Screen time duration (hours/week) | 13.7 (8.8) | 10.6 (6.6) | 13.2 (7.2) | 14.6 (8.1) | 18.4 (11.5) |
| Sports club duration (hours/week) | 1.79 (2.22) | 0.85 (1.29) | 1.94 (1.92) | 2.48 (2.24) | 2.53 (3.01) |
| Peer’s lifestyle behavior |
| Fast food consumption (frequency/week) | 1.03 (1.27) | 0.45 (0.29) | 0.51 (0.34) | 0.59 (0.41) | 2.95 (1.51) |
| Screen time duration (hours/week) | 13.9 (4.3) | 10.9 (2.7) | 13.5 (2.5) | 14.7 (3.0) | 18.5 (4.6) |
| Sports club duration (hours/week) | 1.69 (1.02) | 0.78 (0.59) | 1.83 (0.60) | 2.39 (0.77) | 2.36 (1.03) |
