Fatigue and serum testosterone in obstructive sleep apnea patients

Obstructive sleep apnea (OSA)-related fatigue is a common understudied symptom. Fatigue is associated with low serum testosterone level in non-OSA patients. No data are available about this association in OSA patients.

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.

Fifteen OSA patients and 15 control subjects participated. The parameters analyzed were serum testosterone morning concentration, polysomnography parameters, daytime sleepiness (Epworth Sleepiness Scale) and fatigue (Multidimensional Fatigue Inventory). Regression test was applied in order to show predictors 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.

Mean testosterone level was 3.55 ± 0.7 ng/mL in the OSA group, significantly 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 statistically 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 predictor 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.

OSA-related fatigue was strongly associated with serum testosterone, together with OSA severity.