Sleep architecture, slow wave activity and sleep spindles in mild sleep disordered breathing

Objective: A high degree of sleep fragmentation by arousals related to respiratory events would result in an abnormal distribution of slow wave activity (SWA) and a decrease in sleep spindle density in sleep disordered breathing (SDB) patients when compared to controls. Methods: Eighteen mild SDB subjects (6 females and 12 males), aged 18-56 years with (5 < respiratory disturbance index (RDI) < 30/h) were compared to 18 controls (11 female and 7 male) aged 18-52 years. The sleep EEG power density was performed using fast Fourier transform (FFT) analysis and sleep spindle density integrated digital filtering analysis (IDFA). Esophageal pressure monitoring was performed on the third night. Results: Sleep analysis showed a significant higher number of awakenings < 1 min and arousal indexes in total sleep time, in non-REM (NREM) sleep and in slow wave sleep (SWS) than in controls. SWA and theta band decreased significantly from the first to the fourth cycle in both subjects. Theta and sigma bands were significantly lower in patients than in controls, in each sleep cycle and during the whole night. Moreover, the temporal course of SWA showed an exponential decay in both patients and controls but the time constant of the curve was significantly slower in patients than in controls. Furthermore, in both groups, the sleep spindle index was significantly lower in both SWS and stage 2 in patients than in controls. Conclusions: Sleep architecture in mild SDB subjects is characterized by a high degree of sleep fragmentation resulting in a different time course of SWA and a decreased sleep spindle index when compared to controls. (C) 2002 International Federation of Clinical Neurophysiology. Published by Elsevier Science Ireland Ltd. All rights reserved.