Longer nightly use of continuous positive airway pressure (CPAP) treatment allows a large percentage of patients with severe obstructive sleep apnea (OSA) function more normally during the day, according to a report in the medical journal Sleep.

Patients with OSA experience numerous episodes in which they stop breathing at night, causing frequent sleep disturbances. Consequently, OSA patients are often sleep deprived, which prevents them from functioning normally during the day.

To provide CPAP, which is considered the most effective OSA treatment, the patient wears a facemask through which a device delivers pressurized air to keep the airways open during sleep.

"The actual need for CPAP in terms of reversing sleepiness is likely to be individually determined," lead author Dr. Terri E. Weaver, from the University of Pennsylvania in Philadelphia, said in a statement.

It cannot be assumed that an individual using CPAP only four hours per night is inadequately treated for daytime sleepiness, but on the other hand "we also cannot assume that the patient is effectively treated," Weaver noted.

"Therefore, it is important to evaluate treatment effectiveness by assessing the level of adherence in conjunction with treatment outcomes."

The study involved 149 patients with severe OSA who underwent sleepiness and functional testing before and after 3 months of CPAP treatment.

Overall, the researchers observed a linear progression of good treatment results that correlated with the duration of CPAP use. Specifically, the number of patients with a normal score on the Epworth Sleepiness Scale increased after up to 4 hours of CPAP. Similarly, the patients' scores on the Sleep Latency Test increased after up to 6 hours of CPAP and scores on the Sleepiness Questionnaire improved with up to 7 hours of CPAP.

The results suggest that the odds of normal daily functioning generally increase with longer duration of CPAP use, the authors conclude. However, it should be noted that some patients achieve normal functioning with relatively limited use of this treatment, they add.