Last Updated: 2009-05-18 8:00:03 -0400 (Reuters Health)

New research suggests that many patients with sleep apnea continue to experience excessive daytime sleepiness despite treatment with continuous positive airway pressure (CPAP).

According to the report in the European Respiratory Journal for May, 6% of CPAP-treated subjects have residual excessive sleepiness, defined as an Epworth Sleepiness Scale score of 11 or higher.

"In France alone," lead author Dr. J-L. Pepin, from CHU de Grenoble, France, said in a statement, "we have 230,000 patients using CPAP. We calculate that at least 13,800 of those have residual daytime sleepiness."

The findings come from a study of 502 patients from 37 sleep centres who were using CPAP for more than 3 hours per night and were available for 1-year follow-up.

On initial analysis, 12.0% of patients had residual excessive sleepiness at 1 year. After adjusting for possible confounders, including restless leg syndrome, major depressive disorder, and narcolepsy, the prevalence of residual excessive sleepiness was 6.0%.

Younger age and more sleepiness at diagnosis both correlated with residual excessive sleepiness, the report indicates. An Epworth Sleepiness Score of 11 or higher prior to CPAP increased the odds of residual excessive sleepiness by 5.3-fold.

In terms of the impact of residual sleepiness on quality of life, the investigators found that subjects with this problem scored two times worse on the emotional and energy domains of the Nottingham Health Profile than did their peers with a full response to CPAP.

Further research, the authors conclude, is needed to determine if the residual excessive sleepiness changes over time, if it is a risk factor for cardiovascular and other diseases, and if pharmacologic agents can affect outcomes.

Eur Respir J 2009;33:1062-1067.