Ultradian sleep cycles: Frequency, duration, and associations with individual and environmental factors-A retrospective study

Christian Cajochen; Carolin Franziska Reichert; Mirjam Münch; Virginie Gabel; Oliver Stefani; Sarah Laxhmi Chellappa; Christina Schmidt

doi:10.1016/j.sleh.2023.09.002

Ultradian sleep cycles: Frequency, duration, and associations with individual and environmental factors-A retrospective study

Sleep Health. 2024 Feb;10(1S):S52-S62. doi: 10.1016/j.sleh.2023.09.002. Epub 2023 Oct 31.

Authors

Christian Cajochen¹, Carolin Franziska Reichert², Mirjam Münch², Virginie Gabel³, Oliver Stefani², Sarah Laxhmi Chellappa⁴, Christina Schmidt⁵

Affiliations

¹ Centre for Chronobiology, Psychiatric Hospital of the University of Basel, Basel, Switzerland; Research Cluster Molecular and Cognitive Neurosciences (MCN), University of Basel, Basel, Switzerland. Electronic address: Christian.cajochen@upk.ch.
² Centre for Chronobiology, Psychiatric Hospital of the University of Basel, Basel, Switzerland; Research Cluster Molecular and Cognitive Neurosciences (MCN), University of Basel, Basel, Switzerland.
³ UR 7480 Vertex, University of Normandie, Caen, France.
⁴ School of Psychology, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, United Kingdom.
⁵ Sleep & Chronobiology Group, GIGA-CRC-In Vivo Imaging Research Unit, University of Liège, Liège, Belgium; Psychology and Neuroscience of Cognition Research Unit (PsyNCog), Faculty of Psychology, Speech and Language, University of Liège, Liège, Belgium.

PMID: 37914631
DOI: 10.1016/j.sleh.2023.09.002

Abstract

Objective: Sleep varies between individuals in response to sleep-wake history and various environmental factors, including light and noise. Here we report on the intranight variation of the ultradian nonrapid eye movement-rapid eye movement (NREM-REM) sleep cycle in 369 participants who have contributed to different laboratory studies from 1994 to 2020 at the Centre for Chronobiology, Basel, Switzerland.

Results: We observed a large interindividual variability in sleep cycle duration, including NREM and REM sleep episodes in healthy participants who were given an 8-hour sleep opportunity at habitual bedtime in controlled laboratory settings. The median sleep cycle duration was 96 minutes out of 6064 polysomnographically-recorded cycles. The number and duration of cycles were not normally distributed, and the distribution became narrower for NREM sleep and wider for REM sleep later in the night. The first cycle was consistently shorter than subsequent cycles, and moderate presleep light or nocturnal noise exposure had no significant effects on ultradian sleep cycle duration. Age and sex significantly affected NREM and REM sleep duration, with older individuals having longer NREM and shorter REM sleep particularly in the end of the night, and females having longer NREM sleep episodes. High sleep pressure (ie, sleep deprivation) and low sleep pressure (ie, multiple naps) altered ultradian sleep cycles, with high sleep pressure leading to longer NREM sleep in the first cycle, and low sleep pressure leading to longer REM sleep episodes. Positive correlations were observed between N2 and NREM duration, and between N1 and REM duration. Weak intrasleep REM sleep homeostasis was also evident in our data set.

Conclusions: We conclude that ultradian sleep cycles are endogenous biological rhythms modulated by age, sex, and sleep homeostasis, but not directly responsive to (moderate levels of) environmental cues in healthy good sleepers.

Keywords: Age; Circadian; Nocturnal transportation noise; Presleep light exposure; REM sleep refractory; Sleep homeostasis.

MeSH terms

Female
Humans
Retrospective Studies
Sleep Deprivation
Sleep Wake Disorders*
Sleep* / physiology
Sleep, REM / physiology