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Table 1 Descriptive characteristics of study participants

From: Daylight saving time as a potential public health intervention: an observational study of evening daylight and objectively-measured physical activity among 23,000 children from 9 countries

   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%)
  1. 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.