Table 2 Descriptive statistics of children and their households participating in the current study
All | Boys | Girls | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Variable | Age at survey† | N | Mean | SD | N | Mean | SD | N | Mean | SD |
Body mass index (kg/m2) | At birth | 45284 | 12.62 | 1.23 | 23542 | 12.65* | 1.23 | 21742 | 12.58* | 1.24 |
1 ½ years | 38422 | 16.33 | 1.45 | 19939 | 16.52* | 1.43 | 18483 | 16.13* | 1.44 | |
2 ½ years | 33672 | 16.09 | 1.45 | 17523 | 16.21* | 1.43 | 16149 | 15.96* | 1.45 | |
3 ½ years | 36146 | 15.75 | 1.33 | 18797 | 15.82* | 1.32 | 17349 | 15.66* | 1.33 | |
4 ½ years | 35097 | 15.48 | 1.36 | 18265 | 15.52* | 1.34 | 16832 | 15.44* | 1.37 | |
5 ½ years | 33057 | 15.38 | 1.50 | 17212 | 15.43* | 1.50 | 15845 | 15.34* | 1.50 | |
Variable | Age at survey † | Unit/category | N | Mean (SD) or % | ||||||
Parents’ annual income | ½ year | (million yen) | 45383 | 5.30 (3.28) | ||||||
4 ½ years | 36922 | 5.77 (3.47) | ||||||||
Sleep hour | ||||||||||
4 ½ years | (hours) | 36026 | 9.9 (0.8) | |||||||
Expense for child | ||||||||||
½ year | (10,000 yen/month) | 44093 | 2‡ (0, 400)‡ | |||||||
4 ½ years | 37347 | 4‡ (0, 447)‡ | ||||||||
Gestational period | -- | 22-36 weeks | 45392 | 5.1 | ||||||
37-41 weeks | 94.1 | |||||||||
≥ 42 weeks | 0.9 | |||||||||
Birth weight | -- | < 1000 g | 45392 | 0.2 | ||||||
1001-1500 g | 0.4 | |||||||||
1501-2500 g | 7.9 | |||||||||
≥ 2501 g | 91.5 | |||||||||
Main parental care provider | ½ year | Mother | 45316 | 92.2 | ||||||
Father | 0.1 | |||||||||
Grandmother | 3.7 | |||||||||
Grandfather | 0.1 | |||||||||
Others | 3.9 | |||||||||
4 ½ years | Mother | 38296 | 40.9 | |||||||
Father | 0.3 | |||||||||
Grandmother | 2.4 | |||||||||
Grandfather | 0.2 | |||||||||
Others | 56.3 | |||||||||
Sibling | ½ year | No sibling | 45392 | 49.6 | ||||||
With sibling | 50.4 | |||||||||
4 ½ years | No sibling | 38715 | 18.7 | |||||||
With sibling | 81.3 | |||||||||
Household member | ½ year | With grandparent (s) and parent(s) | 45392 | 21.6 | ||||||
With both parents | 77.9 | |||||||||
With a parent | 0.4 | |||||||||
Other | 0.1 | |||||||||
4 ½ years | With grandparent(s) and parent(s) | 38715 | 23.0 | |||||||
With both parents | 73.9 | |||||||||
With a parent | 3.0 | |||||||||
Other | 0.2 | |||||||||
Wake-up time | 4 ½ years | Before 7 am | 38634 | 25.1 | ||||||
7 am- | 60.7 | |||||||||
8 am- | 11.0 | |||||||||
9 am- | 1.0 | |||||||||
Irregular | 2.2 | |||||||||
Television watching§ | 4 ½ years | None | 37377 | 1.1 | ||||||
< 1 hour | 15.9 | |||||||||
1 hour | 40.2 | |||||||||
2 hours | 28.1 | |||||||||
3 hours | 10.5 | |||||||||
4 hours | 3.2 | |||||||||
≥ 5 hours | 1.0 | |||||||||
Video game playing | 4 ½ years | None | 37240 | 60.5 | ||||||
< 1 hour | 29.7 | |||||||||
1 hour | 8.5 | |||||||||
2 hours | 1.1 | |||||||||
3 hours | 0.3 | |||||||||
Breakfast | 4 ½ years | Eating regularly | 45392 | 97.7 | ||||||
Eating irregularly | 1.6 | |||||||||
Don’t eat | 0.7 | |||||||||
Lunch | 4 ½ years | Eating regularly | 45392 | 99.4 | ||||||
Eating irregularly | 0.6 | |||||||||
Don’t eat | 0.0 | |||||||||
Dinner | 4 ½ years | Eating regularly | 45392 | 97.4 | ||||||
Eating irregularly | 2.6 | |||||||||
Don’t eat | 0.1 | |||||||||
Snack | 4 ½ years | Eating regularly | 45392 | 90.8 | ||||||
Eating irregularly | 7.9 | |||||||||
Don’t eat | 1.3 | |||||||||