The Relationship Between Chronic Fatigue, Sleep quality, and Melatonin Levels in Sjogren's Syndrome

Background: Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease and majority of pa-tients have fatigue and insomnia. Melatonin has many functions in addition to improving sleep quality and duration.The aim of this study was to explore the relationship between fatigue and insomnia, and the association of melatonin levels with fatigue and insomnia in patients with pSS. Materials and Methods: This cross-sectional cohort study included 116 patients and 27 healthy con-trols. Epworth Sleepiness Scale (ESS), Fatigue Severity Scale (FSS) and SF-36 questionnaires were ob-tained from patients. Melatonin was measured by ELISA from the patients' serum. Results: Patients with pSS exhibited greater fatigue compared to the control group, additionally, pa-tients with somnolence exhibited higher levels of fatigue compared to those without somnolence. The median melatonin level was 239 ng/L (189-460) in patients with fatigue and 266 ng/L (219-552) in patients without fatigue (p=0.11). Patients with and without daytime sleepiness had similar melatonin levels, too. The median melatonin level was 429 ng/L (268-774) in healthy controls compared to 254 ng/L (197-491) in patients with PSS (p=0.0098) The quality of life, as measured by the SF-36, was signif-icantly worse in patients with fatigue across all subgroups compared to those without fatigue. There was no correlation between melatonin levels and the subparameters of the SF-36. Conclusions: Fatigue had a negative impact on both quality of life and sleepiness. Those who experi-enced sleepiness had a poorer quality of life. Early morning serum melatonin levels were lower in PSS patients. There was no significant difference in mean serum melatonin levels between patients with and without fatigue. No correlation was found between serum melatonin levels and quality of life.