Composite Phase Deviation as a marker of circadian disruption in college students: Associations with chronotype, sleep, and light regularity.

Circadian rhythms regulate vital biological processes, including the sleep-wake cycle, and their disruption is associated with adverse health outcomes. This study evaluated circadian misalignment using the Composite Phase Deviation (CPD) derived from 14-day actigraphy and examined its associations with sleep regularity, light exposure, and circadian timing in college students. Forty-six students (70% male) wore wrist actigraphs continuously for two weeks and completed questionnaires (PSQI, MCTQ and MEQ). Chronotype was classified using actigraphy-derived corrected mid-sleep time on free days (aMSFsc), with participants categorized as morning (earliest 25%), intermediate, or evening (latest 25%). Higher CPD was associated with later rest onset (sL5, p < 0.001), lower interdaily stability (IS, p = 0.0016), and lower Sleep Regularity Index (SRI, p < 0.001). aMSFsc was also positively associated with worse sleep quality (PSQI, p = 0.047). Group comparisons showed that evening types exhibited higher CPD than intermediate and morning types and lower SRI than morning types. No group differences were observed for the Light Regularity Index (LRI), although CPD was negatively associated with LRI at lower light thresholds. These findings indicate that CPD is a robust marker of circadian disruption and suggest that evening chronotype students experience greater misalignment and sleep irregularity.