Table 2.
Differences between morning, neither and evening chronotypes in circadian-related variables and academic performance.
| Individual chronotype | P(1) | P(2) | P(3) | Correlation (4) | ||||
|---|---|---|---|---|---|---|---|---|
| Morning-type | Neither-type | Evening-type | r | P | ||||
| (n = 141) | (n = 141) | (n = 144) | ||||||
| Girls (%) | 48.6 | 44.7 | 58.3 | 0.059 | 0.037* | 0.021** | ||
| Characteristics | Mean ± SD | Mean ± SD | Mean ± SD | |||||
| Age (year) | 10 ± 1.18a | 10 ± 1.21a | 10 ± 1.34a | 0.623 | 0.871 | 0.979 | 0.068 | 0.164 |
| Chronotype markers | ||||||||
| Objective assessment | ||||||||
| TAP acrofase (hh:mm) | 14:26 ± 00:19a | 15:08 ± 00:10b | 15:54 ± 00:25c | < 0.001 | < 0.001 | < 0.001 | ||
| Melatonin at 01:00 h (pg/ml) | 29.88 ± 21.26a | 25.03 ± 13.97b | 24.79 ± 17.14b | 0.030 | 0.038 | 0.070 | − 0.124 | 0.013 |
| Subjective assessment | ||||||||
| MCTQ (hh:mm) | 3:50 ± 0:37a | 4:03 ± 0:36b | 4:12 ± 0:44c | < 0.001 | < 0.001 | < 0.001 | 0.225 | < 0.001 |
| Midpoint of food intake (hh:mm) | 14:56 ± 0:16a | 15:03 ± 0:20b | 15:11 ± 0:22c | < 0.001 | < 0.001 | < 0.001 | 0.319 | < 0.001 |
| Daytime activity (%) | 206.32 ± 28.87a | 206.73 ± 25.69a | 198.06 ± 28.17b | 0.015 | 0.008 | 0.074 | − 0.151 | 0.002 |
| Regular habits (%) | 91.49 ± 15.00a | 93.38 ± 15.41a | 85.85 ± 18.42b | < 0.001 | < 0.001 | 0.004 | 0.339 | < 0.001 |
| Light exposition | ||||||||
| Light acrophase (hh:mm) | 13:55 ± 0:22a | 14:20 ± 0:20b | 14:43 ± 0:24c | < 0.001 | < 0.001 | < 0.001 | 0.677 | < 0.001 |
| Light during the day (log lux) | 2.20 ± 0.45ab | 2.35 ± 0.21a | 2.12 ± 0.10b | 0.033 | 0.059 | 0.066 | − 0.163 | 0.072 |
| Light before bed time (log lux) | 0.29 ± 0.19a | 0.35 ± 0.19ab | 0.42 ± 0.19b | 0.022 | 0.030 | 0.048 | 0.285 | 0.002 |
| Sleep variables | ||||||||
| Duration | ||||||||
| Sleep duration (hh:mm) | 9:29 ± 0:38a | 9:20 ± 0:35ab | 9:11 ± 0:42b | 0.001 | 0.007 | 0.001 | − 0.169 | 0.001 |
| Short sleepers (n (%)) | 3(1) | 4(1) | 14(4) | 0.003 | 0.067 | 0.087 | ||
| Circadian Function Index (CFI) | 0.82 ± 0.08a | 0.84 ± 0.05b | 0.81 ± 0.10a | 0.007 | 0.006 | 0.011 | − 0.080 | 0.099 |
| Relative amplitude (RA) | 0.96 ± 0.11ab | 0.99 ± 0.03a | 0.94 ± 0.16b | 0.007 | 0.007 | 0.009 | − 0.144 | 0.003 |
| Interdaily stability (IS) | 0.67 ± 0.14a | 0.71 ± 0.12b | 0.66 ± 0.15a | 0.006 | 0.005 | 0.018 | − 0.061 | 0.212 |
| Sleep characteristics | ||||||||
| Central sleep timing (hh:mm) | 3:20 ± 1:14a | 3:30 ± 1:10a | 4:13 ± 1:07b | < 0.001 | < 0.001 | < 0.001 | 0.356 | < 0.001 |
| Depth of sleep (%) | 82.30 ± 12.94a | 80.33 ± 18.72ab | 76.76 ± 23.25b | 0.044 | 0.039 | 0.020 | − 0.128 | 0.008 |
| Day–night contrast (%) | 90.41 ± 13.83ab | 91.78 ± 12.35a | 88.02 ± 15.77b | 0.074 | 0.081 | 0.221 | − 0.150 | 0.002 |
| Social jet lag | ||||||||
| Social jet lag (hh:mm) | 1:12 ± 0:40a | 1:19 ± 0:38ab | 1:29 ± 0:45b | 0.003 | 0.039 | 0.010 | 0.167 | 0.001 |
| Social jet lag n (% of children) | 12 (3) | 14 (4) | 26 (7) | 0.001 | 0.002 | 0.001 | ||
| Academic performance | ||||||||
| Arts score | 5.96 ± 1.48a | 6. 69 ± 1.20b | 6.84 ± 1.08b | 0.024 | 0.050 | 0.293 | 0.264 | 0.011 |
| Average score | 7.71 ± 1.29a | 7.63 ± 1.34a | 7.70 ± 1.11a | 0.244 | 0.481 | 0.628 | 0.172 | 0.097 |
(1) Differences among chronotypes assessed by ANOVA; (2) Differences among chronotypes assessed by ANCOVA adjusted for sex, age, race, academic year and BMI. (3) Differences among chronotypes assessed using ANCOVA adjusted for sex, age, race, academic year, BMI, and total energy intake. (4) Pearson’s correlation between TAP acrophase and circadian-related variables. *Differences among chronotypes assessed using ANCOVA adjusted for age, race, academic year and BMI; ** Differences among chronotypes assessed using ANCOVA adjusted for age, race, academic year; BMI and total energy intake. Different letters indicate significant differences among chronotypes. MCTQ: Munich Chronotype Questionnaire. Social jet lag = MSF – MSW > 2 h.