Composite Phase Deviation (CPD) is a robust marker of circadian disruption in college students, with evening chronotype students showing greater misalignment and sleep irregularity than morning or intermediate types.
Higher CPD was significantly associated with later rest onset as measured by actigraphy.
Higher CPD was significantly associated with lower interdaily stability (IS), indicating more irregular circadian rhythms.
Higher CPD was significantly associated with lower Sleep Regularity Index (SRI), indicating more irregular sleep patterns.
Later actigraphy-derived corrected mid-sleep time on free days (aMSFsc) was associated with worse subjective sleep quality.
Evening chronotype students exhibited higher CPD than both intermediate and morning chronotype students.
Evening chronotype students had lower Sleep Regularity Index (SRI) compared to morning chronotype students.
No significant group differences in Light Regularity Index (LRI) were observed across chronotype groups.
CPD was negatively associated with Light Regularity Index (LRI) at lower light thresholds.
This research suggests that a measure called Composite Phase Deviation (CPD), calculated from two weeks of wrist-worn activity monitors, can reliably identify disruption in the body's internal clock among college students. Students who had higher CPD scores tended to go to sleep later, had less consistent daily activity patterns, and slept at more irregular times. Students with an 'evening' preference—those who naturally stay up late and wake up late—showed the most circadian disruption and the most irregular sleep schedules compared to 'morning' types. The study also found that students with later natural sleep timing reported worse sleep quality on a standard questionnaire, and that irregular patterns of light exposure were linked to more circadian disruption, particularly at lower light intensity levels. However, there were no significant differences in overall light regularity between chronotype groups, suggesting light exposure patterns may influence circadian disruption in more subtle ways. This research suggests that college students with evening chronotypes are especially vulnerable to circadian misalignment, likely because academic schedules are structured around early morning hours that conflict with their biological clocks. The findings point to a need for both individual-level sleep health interventions and broader structural changes in academic environments—such as later class start times—to better accommodate students whose internal clocks naturally run later.
Guimarães Nogueira M, Umemura G, Vallim J, da Costa Lopes L, D Almeida V, Forner-Cordero A. (2026). Composite Phase Deviation as a marker of circadian disruption in college students: Associations with chronotype, sleep, and light regularity.. Chronobiology international. https://doi.org/10.1080/07420528.2025.2606255