Continuous Positive Airway Pressure (CPAP) is the standard treatment for Obstructive Sleep Apnea (OSA), which may cause excessive daytime sleepiness and serious health problems. A recent study which monitored 149 patients with severe OSA before treatment and again after 3 months of CPAP therapy found that, longer CPAP use (about 7 hours per night) was associated with less daytime sleepiness, fatigue and improved daytime functioning.
SLEEP vol 30 (6)-2007