Predictors of fatigue in obstructive sleep apnea.

OBJECTIVE: The objective of this study was to determine potential inflammatory predictors of fatigue in obstructive sleep apnea (OSA). MATERIALS AND METHODS: Fifty-six women and men untreated OSA patients had their sleep monitored with polysomnography. Fatigue was assessed by the Multidimensional Fatigue Symptom Inventory-Short Form. Depressed mood was assessed by the Center for Epidemiologic Studies-Depression Scale. Blood was drawn to assess circulating levels of Interleukin-6 (IL-6) and soluble tumor necrosis factor receptor I (sTNF-RI). Age, gender, body mass index (BMI), blood pressure, OSA severity, depressed mood, and inflammatory biomarkers were entered into a hierarchical multiple linear regression analysis predicting self-reported fatigue. RESULTS: Approximately 42% of the patients reported significant amounts of fatigue. Higher BMI (p = 0.014), greater depressed mood (p = 0.004), and higher sTNF-RI levels (p = 0.033) were independent predictors of fatigue in the final model (full model R2 = .571; p = .003). Age, gender, blood pressure and apnea severity were unrelated to fatigue. CONCLUSION: The findings suggest that in addition to depressed mood, fatigue in OSA may be associated with increased body weight and elevated levels of the proinflammatory cytokine receptor sTNF-RI. The findings support a linkage between the widely reported fatigue in OSA and a sleep-related component of inflammation.