Chronobiology internationalOct 29, 2026

Classes scheduled by body clock improve sleep, daily rhythms, and grades in first-year medical students

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated Nov 2, 2026

Abstract

A total of 220 incoming medical students were evaluated for circadian misalignment and its impact on academic performance.

Students with high social jetlag (SJL >120 min) were assigned to either a later-start schedule or a standard early-start schedule.
Exam scores were predicted by the objective temperature circadian phase, with a significant negative association observed in early-start participants.
Students categorized as late chronotype in the early-start group scored lower than their early chronotype counterparts.
Late chronotype students in the later-start schedule performed similarly to early chronotype students and exhibited greater circadian stability.
Greater rest-activity stability, blue-light stability, and longer sleep duration were associated with the later-start schedule.

Simplified

University students often experience circadian misalignment with academic schedules, which may impair performance. This study evaluated whether a later-start schedule improves academic outcomes and circadian rhythms in first-year medical students. Incoming students (n = 220) completed the Munich Chronotype Questionnaire; those with high social jetlag (SJL >120 min, n = 71) were randomized into either a later-start schedule (LS; classes ≥10:00 a.m., n = 30) or a standard early-start schedule (ES; 8:00 a.m., n = 41). Actigraphy data were collected from 112 students prior to examinations. Based on the objective temperature circadian phase (TCP) with a median acrophase split at 3:59 a.m. ES participants were categorized asearly (ETCP-ES, n = 41) or late (LTCP-ES, n = 41). All LS participants exhibited a TCP later than 3:59 a.m. and remained LTCP-LS group (n = 30). Associations between scheduling, circadian metrics, and exam scores were analyzed using regression and sex-adjusted ANCOVA. TCP predicted exam scores overall (β = -0.217, p = 0.021), most evidently within ES (β = -0.291, p = 0.008). LTCP-ES students scored lower than ETCP-ES students (p = 0.025). LTCP-LS students performed similarly to ETCP-ES students and showed greater circadian robustness, including higher rest-activity stability (p = 0.031), greater blue-light stability (p = 0.029), and longer sleep duration (p = 0.013).

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Classes scheduled by body clock improve sleep, daily rhythms, and grades in first-year medical students

Abstract

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