FIBROMYALGIA SYNDROME - OVERNIGHT FALLS IN ARTERIAL OXYGEN-SATURATION

PURPOSE: Sleep alterations and muscular changes suggesting hypoxia hav e been reported in fibromyalgia syndrome (FS) pathophysiology. We test ed the hypothesis that patients with FS show falls in the oxygen satur ation of hemoglobin in arterial blood (SaO(2)%) during sleep. PATIENTS AND METHODS: Overnight SaO(2)% was measured by digital pulse oximetry in 28 randomly selected women who met 1990 American College of Rheuma tology criteria for the diagnosis of FS and 15 similar controls. Consi dering the results of pulse oximetry and in order to evaluate the poss ible presence of a sleep apnea syndrome (SAS) as the reason for the no cturnal desaturations, the Epworth Sleepiness Scale (ESS) was mailed t o the patients and controls. Patients and controls who had a score hig her than 10 on the ESS underwent a polysomnographic study. RESULTS: Pa tients with FS showed lower overnight minimum SaO(2)% (85.8 +/- 1.3 ve rsus 90.7 +/- 0.9 in controls, P < 0.05), greater number of desaturati ons (8.3 +/- 1.8 versus 2.7 +/- 0.8 in controls, P < 0.05) and more de saturations/hour (1.3 +/- 0.3 versus 0.4 +/- 0.1 in controls, P < 0.05 ), more night minutes in SaO(2)% <92% (56.3 +/- 12.9 versus 9.1 +/- 3. 8 in controls, P < 0.01) and more minutes in SaO(2)% <90% (14.7 +/- 3. 7 versus 2.4 +/- 1.0 in controls, P < 0.05). There were no differences between patients with FS and controls in ESS scores. Five patients (1 9.2%) in the FS group and 2 (15.4%) in the control group had ESS score s higher than 10. One patient acid 1 control subject showed an apnea-p lus-hypopnea index higher than 5 (13 and 9, respectively) in polysomno graphic study. CONCLUSIONS: Patients with FS showed small overnight fa lls in SaO(2)% and spent more time during the night in SaO(2)% below 9 2% and 90% than did the control group. These alterations that, as a wh ole, are not due to the presence of an associated SAS could be importa nt in FS musculoskeletal pathophysiology.