Table 3.
Baseline characteristics of participants aged 13–15 years by sleep time.
| Sleep Time (h/day) | p Value a | |||||
|---|---|---|---|---|---|---|
| <6 | 6 | 7 | 8 | ≥9 | ||
| Participants (n) | 160 | 675 | 932 | 557 | 115 | |
| Female (%) | 63.8 | 55.4 | 50.0 | 42.9 | 35.7 | <0.0001 |
| Mean age (years) (SD) | 14.6 (0.6) | 14.5 (0.6) | 14.4 (0.6) | 14.3 (0.6) | 14.3 (0.6) | <0.0001 |
| Mean SDQ (SD) | 11.9 (6.6) | 9.9 (6.2) | 9.4 (5.6) | 9.9 (6.3) | 12.6 (7.0) | <0.0001 |
| Current state of health (%) | ||||||
| Very good or good | 35.4 | 46.3 | 53.5 | 54.8 | 45.6 | <0.0001 |
| Normal | 53.2 | 48.1 | 42.8 | 40.3 | 50.0 | |
| Poor or very poor | 11.4 | 5.7 | 3.8 | 4.9 | 4.4 | |
| Adequate sleep (%) | ||||||
| Adequate | 10.6 | 22.9 | 44.1 | 71.0 | 70.4 | <0.0001 |
| Slightly inadequate | 45.6 | 59.1 | 46.2 | 24.1 | 22.6 | |
| Inadequate | 43.8 | 18.0 | 9.8 | 4.9 | 7.0 | |
| Tsunami experience (%) | 14.4 | 14.7 | 11.1 | 14.8 | 12.5 | 0.212 |
| Nuclear reactor accident experience (%) | 51.0 | 42.6 | 42.7 | 42.8 | 37.5 | 0.254 |
| Evacuation to other prefectures (%) | 18.8 | 20.3 | 20.7 | 21.9 | 20.9 | 0.921 |
| Respondent of Q1−6 (%) | ||||||
| Participant | 78.7 | 76.0 | 74.7 | 73.1 | 71.6 | 0.526 |
| Proxy | 21.3 | 24.0 | 25.3 | 26.9 | 28.4 | |
| Respondent of other questions (%) | ||||||
| Mother | 87.4 | 83.9 | 84.6 | 84.1 | 79.0 | 0.294 |
| Father | 10.7 | 13.7 | 13.4 | 13.0 | 14.9 | |
| Other | 1.9 | 2.4 | 2.0 | 2.9 | 6.1 | |
SD, standard deviation; a p values were calculated by a chi-squared test (categorical variables), or ANOVA (continuous variables).