ENERGY-EXPENDITURE IN OBSTRUCTIVE SLEEP-APNEA - EFFECTS OF TREATMENT WITH CONTINUOUS POSITIVE AIRWAY PRESSURE

We examined 24-h energy expenditure (EE) in a chamber for indirect cal orimetry in five male patients with obstructive sleep apnea (OSA) and six snoring control subjects (snorers). The 24-h EE was remeasured in patients with OSA after 3-mo treatment with nasal continuous positive airway pressure (CPAP). Patients with OSA had a greater degree of seve re sleep-breathing disturbance than snorers. Patients with OSA had hig her 24-h EE [39.2 +/- 3.0 vs. 33.9 +/- 2.7 kcal . 24 h(-1) kg fat-free mass (FFM)(-1), P < 0.05], daytime urinary norepinephrine and vanilly lmandelic acid (VMA), and aminoterminal procollagen III peptide (PIIIp ) levels, and they tended to have higher sleeping EE (32.4 +/- 4.1 vs. 26.3 +/- 1.9 kcal . 24 h(-1) . kg FFM(-1), P < 0.1) than snorers. CPA P treatment normalized sleep architecture and breathing. CPAP treatmen t also decreased sleep EE (from 32.4 +/- 4.1 to 27.2 +/- 1.4 kcal . 24 h(-1) . kg FFM(-1), P < 0.05) and EE variability during sleep (from 1 .6 +/- 0.5 to 1.0 +/- 9.5 kcal . 24 h(-1) . kg FFM(-1), P < 0.05) and increased the basal metabolic rate-to-sleep EE ratio in all subjects. Serum PIIIp and plasma norepinephrine decreased after CPAP in all pati ents. We conclude that OSA is associated with an increased sleep EE, w hich is normalized by treatment with CPAP.