Fatigue and serum testosterone in obstructive sleep apnea patients Raluca Mihaela Bercea 1,2 , Traian Mihaescu 1,2 , Cristian Cojocaru 1,2 and Bjørn Bjorvatn 3,4 1 ‘Grigore T. Popa’ University of Medicine and Pharmacy, Iasi, Romania 2 Clinic of Pulmonary Diseases, Iasi, Romania 3 Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway 4 Norwegian Competence Center for Sleep Disorders, Haukeland University Hospital, Bergen, Norway Abstract Introduction: Obstructive sleep apnea (OSA)-related fatigue is a common under- studied symptom. Fatigue is associated with low serum testosterone level in non- OSA patients. No data are available about this association in OSA patients. Objectives: To investigate in adult obese males affected by OSA, the relationship between fatigue and serum testosterone in order to identify predictors for OSA- related fatigue. Methods: Fifteen OSA patients and 15 control subjects participated. The param- eters analyzed were serum testosterone morning concentration, polysomnography parameters, daytime sleepiness (Epworth Sleepiness Scale) and fatigue (Multidi- mensional Fatigue Inventory). Regression test was applied in order to show pre- dictors of fatigue. Kruskal–Wallis test followed by post-hoc analysis was performed to test for differences between controls and OSA subgroups for testosterone, fatigue components and sleepiness. Results: Mean testosterone level was 3.55 ± 0.7 ng/mL in the OSA group, signifi- cantly lower than in controls (4.26 ± 1.1 ng/mL, P = 0.049). An inverse correlation was found between testosterone and fatigue scores (P < 0.01). Furthermore, a sta- tistically significant difference was found between the control group and the severe OSA subgroup for general fatigue, physical fatigue, reduced activity and mental fatigue. However, no significant differences were found between controls and mild OSA. Among all variables, testosterone was the only independent significant pre- dictor of physical fatigue (t =-2.56, P = 0.033, R = 0.978, R 2 = 0.958) and reduced activity (t =-4.41, P = 0.002, R = 0.966, R 2 = 0.934) in the OSA patients. Conclusions: OSA-related fatigue was strongly associated with serum testosterone, together with OSA severity. Please cite this paper as: Bercea RM, Mihaescu T, Cojocaru C and Bjorvatn B. Fatigue and serum testosterone in obstructive sleep apnea patients. Clin Respir J 2014; ••: ••–••. DOI:10.1111/crj.12150. Key words fatigue – obstructive sleep apnea – sleepiness – testosterone Correspondence Raluca Mihaela Bercea, MD, PhD, ‘Grigore T. Popa’ University of Medicine and Pharmacy, Clinic of Pulmonary Diseases, 30 Dr. I. Cihac Street, 700115 Iasi, Romania. Tel: 0047 46575799 Fax: 0040 332815550 email: ralbercea@yahoo.com Received: 27 February 2013 Revision requested: 15 March 2014 Accepted: 08 April 2014 DOI:10.1111/crj.12150 Authorship and contributorship R.M. Bercea and T. Mihaescu designed the study and performed research; R.M. Bercea and C. Cojocaru collected data and performed the statistics; C. Cojocaru, T. Mihaescu and B. Bjorvatn provided input for the tables and figures; R.M. Bercea and B. Bjorvat analyzed data and wrote the paper. All authors have seen and approved the final version of the manuscript. Ethics All subjects gave written informed consent prior to their inclusion in the study, and the study was approved by the local ethical committee in accordance with the standards laid down in the Declaration of Helsinki. Conflict of interest The authors (R.M.B., T.M., C.C. and B.B.) have stated explicitly that there are no conflicts of interest in connection with this article. The Clinical Respiratory Journal ORIGINAL ARTICLE 1 The Clinical Respiratory Journal (2014) • ISSN 1752-6981 © 2014 John Wiley & Sons Ltd