Individuals with OSA can experience up to 300 sleep disruptions each night, which may result in excessive daytime sleepiness (EDS), one of the most common symptoms of OSA. EDS can have serious consequences, including motor vehicle accidents, poor school performance, and work-related accidents and performance issues. The most common treatment for OSA is CPAP therapy. This involves wearing a mask over the nose while sleeping; air then flows through the mask into the nose to maintain a level of pressure that keeps the breathing passages open. CPAP therapy typically results in fewer sleep and breathing disruptions during the night, which may increase an individual's alertness levels during the day. The purpose of this study is to evaluate the relationship between severity of sleep-disordered breathing and daytime alertness levels in adults with and withoutout symptoms of OSA.