Polygraphic recording includes nasal air flow, snore train, thoracic and abdominal effort, oxyhemoglobin saturation, and determination of the body position. Recordings will be used in further investigations if at least 4 h of data can be obtained. EEG sleep data will include 6 EEG channels (F3-A2, F4-A1, C3-A2, C4-A1, O1-A2, O2-A1) according to the 10/20 system, 2 electrooculogram (EOG) channels (left/right), submental electromyogram (EMG) and tibialis anterior electromyogram from both legs (EMG) and will be scored manually.