Table 1.
Participant demographics for analytic sample
| Control | Intervention | |
|---|---|---|
| N | 23 | 23 |
| Age (years) | 16.5 ± 0.8 | 16.0 ± 0.8 |
| (14.5–17.9) | (15.2–17.9) | |
| Sex (N) | ||
| Females | 13 | 11 |
| Males | 10 | 12 |
| Ancestry (N) | ||
| African-American | 6 | 12 |
| White | 14 | 6 |
| Multiple | 3 | 2 |
| Other | 0 | 3 |
| Ethnicity (N) | ||
| Non-Hispanic | 12 | 17 |
| Hispanic | 11 | 6 |
| High school grade (N) | ||
| 9th | 3 | 1 |
| 10th | 9 | 9 |
| 11th | 8 | 10 |
| 12th | 3 | 3 |
| Leave home for school (clock time) | ||
| Mean ± SD | 07:10 ± 00:40 | 07:03 ± 00:23 |
| (earliest–latest) | (05:50–07:50) | (06:30–07:45) |
| School start (clock time) | ||
| Mean ± SD | 07:47 ± 00:39 | 07:52 ± 00:20 |
| (earliest–latest) | (06:30–09:30) | (07:00–08:25) |
| Morningness scorea | 30.9 ± 4.6 | 32.4 ± 6.3 |
| Mid-sleep on free days (MSFsc)b,c | 05:08 ± 01:14 | 04:48 ± 01:37 |
| Mid-sleep on school daysb | 03:12 ± 00:26 | 03:06 ± 00:30 |
| Social jetlag (h)b,c,d | 3.1 ± 0.9 | 2.9 ± 1.2 |
| Depressive symptomse | 8.5 ± 5.4 | 11.3 ± 5.9 |
aSmith Morningness Questionnaire.
bMunich ChronoType Questionnaire (MCTQ).
cOnly those without alarm use on free days were included (N = 18 in Control group; N = 21 in Intervention group).
dSocial jet lag = the difference between mid-sleep on free days and mid-sleep on school days.
eCenter for Epidemiologic Studies Depression (CES-D) Scale.