Figure 2

Developmental changes in chronotype (ΔChronotype) during adolescence is associated with both school timings and students’ baseline chronotype. (a) Baseline chronotype tertile affects the change in Chronotype from 1st to 5th year. Those students on the earliest tertile delayed their chronotype by their 5th year, independently on school timing (from 04:11 to 05:08, from 04:47 to 06:38, from 05:08 to 06:58, for morning-, afternoon- and evening- attending students respectively). Students on the latest tertile of MSFsc, on the other hand, did not delay or even advanced their chronotypes (from 07:20 to 06:07, from 07:34 to 07:29, from 07:59 to 08:03, for morning-, afternoon- and evening- attending students respectively). (b) ΔChronotype correlates with baseline chronotype and school timing. Students with a late baseline MSFsc experienced a lower chronotype change from 1st to 5th year. Particularly, the slope of the relationship between ΔChronotype and baseline chronotype indicates that, when the baseline chronotype is 1-h later, the age-related changes on chronotype are lower: 43 min (95% CI = − 53 to − 32 min), 49 min (95% CI = − 61 to − 38 min) and 32 min (95% CI = − 44 to − 20 min) for morning-, afternoon- and evening-attending students, respectively. N = 259. ΔChronotype = MSFsc 5th year—MSFsc 1st year. Baseline chronotype = MSFsc in 1st year. Color indicates school timing: yellow, green and blue for morning, afternoon and evening, respectively.