Purpose of review: Although continuous positive airway pressure (CPAP) treatment effectively reduces sleepiness in obstructive sleep apnea (OSA) patients, some patients remain sleepy in spite of proper treatment. After exclusion or treatment of known causes of sleepiness, residual sleepiness may be diagnosed. Recent changes in approval for currently available wakefulness stimulants in Europe, development of new stimulants and questions about the reality of residual sleepiness prompted this review.
Recent findings: Prevalence of residual sleepiness is approximately 10% and clearly decreases with increased nightly use of CPAP. Before treatment, patients with residual sleepiness are younger, suffer from less severe OSA and have worse health perception and mood than patients who respond to CPAP. Residual sleepiness is accompanied by other residual symptoms (e.g. fatigue, poor quality of life), suggesting the existence of a 'CPAP resistant syndrome'. Pathophysiological mechanisms remain unclear. Stimulant medication may be beneficial in some patients and is well tolerated.
Summary: In spite of a substantial prevalence, residual sleepiness remains still poorly understood and may be difficult to treat. There remains a need for large prospective studies to better define predictive baseline characteristics and further research on causal mechanisms and pharmacological treatments, including large, long-term clinical trials of wakefulness stimulants, is needed.