Figure 1

Longitudinal changes in Chronotype, Social jetlag and Sleep duration during adolescence. (a) Mean changes on Chronotype depend on school timing and age. Evening-attending students exhibit later MSFsc than their morning-attending peers: 47 min in 1st year (06:33 vs. 05:46) and it doubles to 104 min in 5th year (07:28 vs. 05:44). Afternoon-attending students show a similar pattern in 5th year: 82 min later MSFsc than their morning-attending peers (07:08 vs. 05:46). Post-hoc pairwise comparisons, P < 0.006 (Bonferroni-corrected P < 0.05). (b) SJL depends on school timing. SJL levels are lower for evening-attending students than for their afternoon-attending peers, both in 1st year (1.68 h vs. 2.16 h) and in 5th year (1.80 vs. 2.20). The same happens when compared to morning-attending students, who present the highest SJL levels (3.70 h and 3.40 h in 1st and 5th year, respectively). No significant differences were found between 1st and 5th year at any school timing. Post-hoc comparisons, P < 0.017 (P < 0.05, Bonferroni corrected). (c) School timing and age affect sleep duration on weekdays (SDw) but not on free days (SDf). On weekdays, adolescents sleep less in their 5th year regardless of their school timing, and in the morning school timing regardless of their age. Students sleep more on free days than on weekdays independently of their age and school timing. No differences were found between school timings and age on free days. The interaction between school timing and age was not significant. The asterisk (*) indicates significant difference in sleep duration between 1st and 5th year across school timings, which was found on weekdays but not on free days. Post-hoc comparisons, P < 0.0038 (P < 0.05, Bonferroni corrected). Data are Mean ± s.e.m. N = 259. Lowercase letters indicate significant differences between groups: (a) compared with morning of the same school year; (b) compared with afternoon of the same school year; (c) compared with evening of the same school year; (d) compared with 1st year of the same school timing; (e) compared with 5th year of the same school timing; (f) compared with morning, across age groups; (g) compared with afternoon, across age groups; (h) compared with evening, across age groups.