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

• Published in: Scientific reports Vol. 7; no. 1; pp. 3216 - 13
• Main Authors: Phillips, Andrew J. K., Clerx, William M., O’Brien, Conor S., Sano, Akane, Barger, Laura K., Picard, Rosalind W., Lockley, Steven W., Klerman, Elizabeth B., Czeisler, Charles A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12.06.2017; Nature Publishing Group; Nature Portfolio
• Subjects: 13/51; 631/443/376; 631/477/2811; 639/705/1042; 9/10; Academic achievement; Academic Performance - standards; Adolescent; Biological clocks; Circadian rhythm; Circadian Rhythm - physiology; Circadian rhythms; Female; Humanities and Social Sciences; Humans; Light; Male; Mathematical models; Melatonin; Melatonin - metabolism; Models, Theoretical; multidisciplinary; Photometry; Science; Science (multidisciplinary); Sleep - physiology; Sleep - radiation effects; Sleep and wakefulness; Sleep Disorders, Circadian Rhythm - physiopathology; Time Factors; Wakefulness - physiology; Wakefulness - radiation effects; Wrist; Young Adult
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-017-03171-4

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.