Neurocognitive function in patients with residual excessive sleepiness from obstructive sleep apnea: a prospective, controlled study.

OBJECTIVE: This study aimed to evaluate neurocognitive function in adult patients with residual excessive sleepiness (RES) after appropriate treatment of obstructive sleep apnea (OSA) with CPAP and good adherence to treatment. METHODS: This was a prospective controlled study. We included patients of both sexes, aged 35-60 years with OSA and an apnea-hypopnea index >20 ev/h, effectively treated with CPAP, but with a residual Epworth Sleepiness Scale score ≥11. The control group consisted of OSA patients adequately treated with CPAP who did not present with excessive sleepiness after treatment. Both groups underwent the following evaluations: polysomnography, multiple sleep latency testing, depression symptoms, and cognitive assessment. RESULTS: Regarding baseline characteristics, the data were matched for age, years of study, and body mass index. Long-term memory result did not show a significant difference between the two groups (RES group 4.7 ± 2.0; control group 6.5 ± 1.9; p = 0.08). The executive functions were the most affected, with alterations in Wisconsin test, number of categories (RES group: 1.6 ± 1.4; control group: 3.0 ± 1.4; p = 0.01), and semantic verbal fluency test (RES group: 13.6 ± 3.3; control group: 16.9 ± 4.3; p = 0.04). CONCLUSION: In summary, the mean depression scale score in the group with residual excessive sleepiness was significantly higher than that in the control group. Patients with residual excessive sleepiness showed impairment of executive functions but no impairments in other cognitive domains.

The cholinergic system may play a role in the pathophysiology of residual excessive sleepiness in patients with obstructive sleep apnea.

Obstructive sleep apnea (OSA) is a prevalent condition characterized by momentary cessations in breathing during sleep due to intermittent obstruction of the upper airway. OSA has been frequently associated with a number of medical comorbidities. CPAP (continuous positive airway pressure) is the gold standard treatment and is known to improve OSA symptoms, including excessive sleepiness. However, 12-14% of CPAP-treated patients continue to complain of sleepiness despite normalization of ventilation during sleep, and 6% after exclusion of other causes of EDS. This is of great concern because EDS is strongly associated with systemic health disorders, lower work performance, and a high risk of accidents. We hypothesized that decreased central cholinergic activity plays a role in the pathophysiology of residual excessive sleepiness in patients with OSA treated with CPAP. Acetylcholine (Ach) plays a large role in wakefulness physiology, and its levels are reduced in sleepiness. Herein, we discuss the potential role of the cholinergic system in this new clinical condition.