Irregular sleep/wake patterns are associated with poorer academic performance and delayed circadian and sleep/wake timing

Andrew J K Phillips,Conor S O’Brien,William M Clerx,Rosalind W Picard,Elizabeth B Klerman,Steven W Lockley,Akane Sano,Laura K Barger,Charles A Czeisler

doi:10.1038/s41598-017-03171-4

Abstract

The association of irregular sleep schedules with circadian timing and academic performance has not been systematically examined. We studied 61 undergraduates for 30 days using sleep diaries, and quantified sleep regularity using a novel metric, the sleep regularity index (SRI). In the most and least regular quintiles, circadian phase and light exposure were assessed using salivary dim-light melatonin onset (DLMO) and wrist-worn photometry, respectively. DLMO occurred later (00:08 ± 1:54 vs. 21:32 ± 1:48; p < 0.003); the daily sleep propensity rhythm peaked later (06:33 ± 0:19 vs. 04:45 ± 0:11; p < 0.005); and light rhythms had lower amplitude (102 ± 19 lux vs. 179 ± 29 lux; p < 0.005) in Irregular compared to Regular sleepers. A mathematical model of the circadian pacemaker and its response to light was used to demonstrate that Irregular vs. Regular group differences in circadian timing were likely primarily due to their different patterns of light exposure. A positive correlation (r = 0.37; p < 0.004) between academic performance and SRI was observed. These findings show that irregular sleep and light exposure patterns in college students are associated with delayed circadian rhythms and lower academic performance. Moreover, the modeling results reveal that light-based interventions may be therapeutically effective in improving sleep regularity in this population.

Highlights

The sleep of college students is often variable in both duration and timing, with many students suffering from considerable sleep deficiency[1,2,3,4,5]
In this population of students living under real-world academic and social constraints, there was no correlation between average daily sleep duration and Sleep Regularity Index (SRI) (r = 0.05, p = 0.71)
Our findings demonstrate that irregular sleep schedules in a specific population of college students are associated with a significant circadian phase delay in the timing of both the endogenous melatonin rhythm and in the sleep propensity rhythm—equivalent to traveling two to three time zones westward—compared to students on a more regular sleep/wake schedule

Summary

Introduction

The sleep of college students is often variable in both duration and timing, with many students suffering from considerable sleep deficiency[1,2,3,4,5]. The index is scaled so that an individual who sleeps and wakes at exactly the same times each day scores 100, whereas an individual who sleeps and wakes at random scores 0 This index is constructed on the reasoning that changes in sleep schedules from one 24-h interval to the may cause circadian disruption and impact normal biological functioning and health. The difference in circadian timing could be due to different patterns of light exposure associated with Regular vs Irregular sleepers, because light exposure during the early biological night delays the circadian clock[29]. We tested these mechanistic hypotheses using a previously-validated mathematical model of the human circadian clock and its response to light

Methods

Results

Conclusion