Polysomnography and polygraphy will be performed by a trained staff member using the Somnomedics Diagnostic Systems (SOMNOmedics GmbH, Germany). Patients will be studied in their hospital beds. Polygraphic and polysomnographic all-night recordings according to AASM standard criteria will be obtained between approximately 22.00 (lights-out) and 6.00 am (buzzer or alarm clock). Thus, time in bed (TIB) is fixed with 7.5 hours.