Impact of overnight sleep on resting metabolic rate in OSA patients and controls

Introduction Obstructive sleep apnea (OSA) syndrome has been previously associated with sympathetic overactivity, hormonal dysregulation and metabolic abnormalities. Aim To investigate the potential variation of resting metabolic rate (RMR) just before and after an overnight sleep, in patients with OSA and in non-OSA controls. Material-Methods This is a nested case-control study. From a consecutive population referred for sleep evaluation between June 2007 and December 2011, subjects with OSA constituted the group of patients and subjects without OSA or other sleep disorders, the group of controls. All patients underwent anthropometric measurements, night polysomnography and evaluation of resting metabolic rate (RMR) before and after nocturnal sleep. RMR was compared before and after sleep in each group utilizing paired t-test or Wilcoxon signed rank test, according to distribution of values; level of p>0.05 was considered significant. Results The study population constituted of 158 OSA patients (58.2% male; 46.7±12.2 years old) and 20 controls (90% male; 51.3±11.7 years old). In OSA patients RMR measured before and after overnight sleep was significantly different (1869.8±869.5 vs. 1709.6±685.9, p 30/h) but not in the ones with mild (AH=5-15/h) syndrome. In controls no difference was noted in RMR before and after overnight sleep (1416.4±501.4 vs. 1344.2±565.2, p=0.279). Conclusion Patients with moderate or severe OSA establish a significant variation in RMR before and after overnight sleep, compared to non-OSA controls.