Endocrine biomarkers related to sleep-wake cycle and sleep disturbances in patients with bipolar disorder: A systematic review

Abstract

Introduction Sleep and circadian disturbances have been widely studied in patients with bipolar disorder (BD) (Duarte Faria et al., 2015; Gonzalez, 2014). However, there is no clear evidence about the role of peripheral biomarkers of circadian cycle in this population. Objectives This systematic review aims to identify potential endocrine biomarkers of circadian rhythm in blood and study their relationship with sleep problems in BD. Methods An electronic search of Pubmed and PsycoInfo databases were performed. It includes articles about the topic from 1991 to 2021. The search strategy was: (“Peripheral biomarkers” OR “biological markers” OR biomarker OR cortisol OR melatonin OR orexin OR hypocretin) AND (blood OR serum OR plasma) AND (“sleep-wake” OR “circadian rhythm” OR sleep OR insomnia) AND “bipolar”. Results 92 records were obtained after excluding duplicates. Only five studies met the inclusion criteria (n = 499; BD = 125; unipolar depression = 148; schizophrenia = 80; controls = 146). The endocrine parameters analyzed were: cortisol (3 studies), melatonin (1 study) and orexin-A (1 study). Overall, no significant associations between these biomarkers and sleep disturbances, assessed with subjective (psychometric evaluation) and/or objective (polysomnography) measures, were detected. Conclusions This systematic review highlights the lack of studies that explores the role of endocrine biomarkers related to circadian function in the pathophysiology of sleep disturbances in BD. Disclosure No significant relationships.

Keywords

• circadian rhythms
• sleep disorders
• orexin
• melatonin