Excessive daytime sleepiness in obstructive sleep apnea patients after home CPAP treatment: A long-term outcome study

Previous studies have been inconclusive about the improvement in excessive daytime sleepiness (EDS) after continuous positive airway pressure (CPAP) treatment. One hundred and thirty-one obstructive sleep apnea patients, who were on regular home CPAP treatment, were investigated with an overnight polysomnography and daytime multiple sleep latency test (MSLT). Their Epworth Sleepiness Scale (ESS) scores and mean sleep latencies (MSL) before and after treatment were compared. With a mean duration of CPAP treatment for 3.4 +/- 2.4 years, improvement in both ESS (12.8 to 9.95) and MSLT (7.32 to 8.92 min) were found (P < 0.001). Residual EDS was found in 38.5% (20 out of 52) and 66.2% (51 out of 77) of subjects, measured by ESS (>= 14) and MSL (< 8 min), respectively. Higher body mass index was found in those subjects with persistently shortened post-CPAP MSL of < 8 min. Our findings suggested that EDS was a reversible symptom in some but not all OSAS patients. Whilst residual EDS could partly be accounted for by underlying obesity, the persistence of a shortened MSLT and sleep-onset REM period could be the result of underlying genetic factors and/or scarring effect due to hypoxic related neuronal damages.