Table 1.
Baseline characteristics of participants aged 4–6 years by sleep time.
| Sleep Time (h/day) | p Value a | ||||
|---|---|---|---|---|---|
| <9 | 9 | 10 | ≥11 | ||
| Participants (n) | 191 | 1368 | 1530 | 294 | |
| Female (%) | 51.3 | 48.6 | 49.5 | 51.7 | 0.742 |
| Mean age (years) (SD) | 5.2 (0.8) | 5.1 (0.8) | 4.9 (0.8) | 4.7 (0.8) | <0.0001 |
| Mean SDQ (SD) | 13.1 (6.4) | 11.7 (5.6) | 11.7 (5.7) | 12.0 (5.7) | 0.012 |
| Current state of health (%) | |||||
| Very good or good | 47.1 | 55.1 | 57.8 | 51.0 | 0.054 |
| Normal | 51.3 | 43.4 | 40.3 | 47.3 | |
| Poor or very poor | 1.6 | 1.6 | 1.9 | 1.7 | |
| Napping time (%) | |||||
| None | 44.4 | 56.7 | 71.8 | 82.6 | <0.0001 |
| <1 hour/day | 2.7 | 1.8 | 1.8 | 1.0 | |
| 1−2 hours/day | 25.9 | 22.5 | 16.5 | 11.3 | |
| ≥2 hours/day | 27.0 | 18.9 | 9.9 | 5.1 | |
| Tsunami experience (%) | 8.4 | 9.7 | 9.4 | 10.2 | 0.914 |
| Nuclear reactor accident experience (%) | 39.3 | 33.9 | 34.3 | 39.1 | 0.188 |
| Evacuation to other prefectures (%) | 15.7 | 27.3 | 39.3 | 47.3 | <0.0001 |
| Respondent (%) | |||||
| Mother | 88.5 | 91.6 | 92.8 | 91.5 | 0.206 |
| Father | 10.5 | 7.5 | 5.8 | 7.5 | |
| Other | 1.1 | 1.0 | 1.4 | 1.0 | |
SD, standard deviation; a p values were calculated by a chi-squared test (categorical variables), or ANOVA (continuous variables).