Table 1.
Descriptive characteristics of study participants
| N (%) participants | N (%) valid days | ||
|---|---|---|---|
| Full sample | 23,188 (100%) | 158,784 (100%) | |
| Sex | Male | 8819 (38%) | 62,745 (40%) |
| Female | 14,369 (62%)† | 96,039 (60%) | |
| Age | 5-6 years | 1800 (8%) | 7855 (5%) |
| 7-8 years | 711 (3%) | 4963 (3%) | |
| 9-10 years | 5769 (25%) | 30,702 (19%) | |
| 11-12 years | 9616 (41%) | 61,352 (39%) | |
| 13-14 years | 4206 (18%) | 46,530 (29%) | |
| 15-16 years | 1086 (5%) | 7382 (5%) | |
| Country [No. studies] | Australia [N = 2] | 2459 (11%) | 18,679 (12%) |
| Brazil [N = 1] | 453 (2%) | 1577 (1%) | |
| Denmark [N = 2] | 2031 (9%) | 11,030 (7%) | |
| England [N = 4] | 10,284 (44%) | 83,420 (53%) | |
| Estonia [N = 1] | 656 (3%) | 2537 (2%) | |
| Madeira [N = 1] | 1214 (5%) | 4899 (3%) | |
| Norway [N = 1] | 384 (2%) | 1459 (1%) | |
| Switzerland [N = 1] | 404 (2%) | 2569 (2%) | |
| United States [N = 2] | 5303 (23%) | 32,614 (21%) | |
| Weight status | Normal/underweight | 17,573 (76%) | 121,350 (76%) |
| Overweight | 4116 (18%) | 27,967 (18%) | |
| Obese | 1499 (6%) | 9467 (6%) | |
| Mother’s education | Up to high school | 7422 (48%) | 54,547 (48%) |
| College/vocational | 2656 (17%) | 19,352 (17%) | |
| University level | 5251 (34%) | 38,723 (34%) |
For individuals measured more than once, the first column gives age and weight status at baseline while the second column gives age and weight status during the measurement period in question. Numbers add up to less than the total for mother’s education because this variable was only collected in 11 of the 15 studies, and was also subject to some missing data within those 11 studies (see Additional file 1: Tables A1 and A2). †Proportion of girls 52% after excluding one large American study that measured girls only.