Investigating the Link between Circadian Clock Gene Expressions, Chronotype, Insomnia, and Daytime Sleepiness in Patients with Obstructive Sleep Apnea

Abstract

Introduction. This study aimed to investigate the relationship between obstructive sleep apnea (OSA), circadian rhythms, and individual sleep–wake preferences, as measured by chronotype, and to assess the association between circadian clock gene expression and subjective sleep-related variables. Methods: A total of 184 individuals were recruited, underwent polysomnography (PSG), and completed questionnaires including a chronotype questionnaire (CQ), insomnia severity index (ISI), and Epworth sleepiness scale (ESS). Blood samples were collected in the evening before and morning after PSG. Gene expression analysis included BMAL1, CLOCK, PER1, CRY1, NPAS2, and NR1D1. Results: In the OSA group, the subjective amplitude (AM score of CQ) positively correlated with all circadian clock genes in the morning (R ≥ 0.230 and p < 0.05 for each one), while the morningness–eveningness (ME score of CQ) was only associated with the evening BMAL1 level (R = 0.192; p = 0.044). In healthy controls, insomnia severity correlated with evening expression of BMAL1, PER1, and CRY1. Conclusions: The findings highlight the complex interplay between OSA, circadian rhythms, and sleep-related variables, suggesting potential determinants of morning chronotype in OSA and implicating disrupted circadian clock function in subjective feelings of energy throughout the day. Further research is warranted to elucidate underlying mechanisms and guide personalized management strategies.