Gender differences in obstructive sleep apnea with comorbid treatment-resistant depression

Abstract Background A bidirectional relationship between major depression and obstructive sleep apnea (OSA) has been established, suggesting the possibility of overlapping and compounding disease processes. Depression, however, while more prevalent in women, is a highly heterogeneous disorder and can be difficult to treat regardless of gender. A common overlapping symptom of depression and OSA is fatigue. Gender differences in OSA symptomatology (and fatigue in particular) are also consistently observed. Here, we investigate OSA in specific relation to treatment-resistant depression. Methods A cross-sectional exploratory design was used to analyse data from 94 patients with treatment-resistant depression from a subspecialist mood disorders outpatient service who had no previous sleep assessment. Participants completed overnight polysomnography and a battery of rating scales assessing mood, sleep, and daytime functioning. Linear regression models determined whether presence of fatigue in treatment-resistant depression predicted OSA severity. Results There was a high prevalence (79%) of previously undiagnosed OSA in our sample of patients with treatment-resistant depression. Treatment-resistant depression was one factor to close the gap in obstructive sleep apnea prevalence between men and women in this group. Presence of OSA measured objectively by the Apnea Hypopnea Index was not associated with episode state (depressed vs. euthymic). Daytime sleepiness scores as measured by the Epworth Sleepiness Scale indicated higher than normal daytime sleepiness with no difference between genders. Men and women in our study reported similar amounts of fatigue as measured by the Profile of Mood States-Fatigue Subscale, however, daytime fatigue (but not sleepiness) predicted OSA severity in women only. Conclusions We argue that typical symptoms of treatment-resistant depression may overshadow key symptoms of undetected OSA. Specifically, we found that daytime fatigue may be one factor masking a potentially significant underlying sleep disorder in women only. Comprehensive assessment and screening for sleep apnea in patients with treatment-resistant depression is encouraged, and the importance of investigating severity of fatigue in this population is emphasized.