The contribution of fatigue and sleepiness to depression\ud in patients attending the sleep laboratory for evaluation\ud of obstructive sleep apnea

Purpose: A high prevalence of depressive symptomatology\ud has been reported amongst sufferers of obstructive sleep\ud apnea (OSA), but it remains unclear as to whether this is\ud due to their OSA or other factors associated with the\ud disorder. The current study aimed to assess the incidence\ud and aetiology of depression in a community sample of\ud individuals presenting to the sleep laboratory for diagnostic\ud assessment of OSA.\ud Methods: Forty-five consecutive individuals who presented to\ud the sleep laboratory were recruited; of those, 34 were\ud diagnosed with OSA, and 11 were primary snorers with no\ud clinical or laboratory features of OSA. Nineteen control\ud subjects were also recruited. Patients and controls completed\ud the Beck Depression Inventory, the Profile of Mood States\ud (POMS), and the Epworth Sleepiness Scale to assess their\ud mood and sleepiness, prior to their polysomnography.\ud Results: All patients reported significantly more depressive\ud symptoms compared with healthy controls, regardless of their degree of OSA. There were no significant differences\ud between OSA patients and primary snorers on any of the\ud mood and self-rated sleepiness measures. Depression scores\ud were not significantly associated with any of the nocturnal\ud variables. Regression analysis revealed that the POMS\ud fatigue subscale explained the majority of the variance in\ud subjects' depression scores.\ud Conclusions: Fatigue was the primary predictor of the level\ud of depressive symptoms in patients who attended the sleep\ud laboratory, regardless of the level of severity of sleep disordered breathing. When considering treatment options,\ud practitioners should be aware of the concomitant occurrence\ud of depressive symptoms and fatigue in patients presenting with sleep complaints, which may not be due\ud to a sleep disorder