Long-term evolution of daytime somnolence in patients with sleep apnea/hypopnea syndrome treated by continuous positive airway pressure.

We demonstrated in a previous study that excessive daytime sleepiness (EDS) in patients who have sleep apnea/hypopnea syndrome (SAHS) and are undergoing continuous positive airway pressure (CPAP) treatment improved differently in two groups of patients: in group I, multiple sleep latency tests (MSLT) were normalized after 50 days of treatment (individual value > 10 minutes), whereas they remained low (individual value < 10 minutes) in group II, with a significant difference between groups. To evaluate the long-term evolution of daytime somnolence under nasal CPAP treatment, five patients from group I and seven patients from group II underwent a new polysomnography and MSLT 4 years after the previous study. Clinical, polysomnographic and MSLT results obtained at baseline before treatment (T1), after the initial 50-day period of CPAP treatment (T2), and after 4 years (T3) were compared. The significant difference in mean MSLT value between the two groups previously observed at T1 and T2 disappeared at T3 (group I: 12.4+/-5.9 minutes; group II: 9.7+/-5.9 minutes). We found that this long-term improvement in excessive daytime somnolence was independent of the initial MSLT value, the severity of SAHS, and the initial MSLT changes under nasal CPAP. Long-term MSLT evolution was significantly correlated to CPAP compliance. These results demonstrate that even in the absence of a significant increase in MSLT at the beginning of CPAP treatment, further improvement is still possible several years later, which may encourage the regular, long-term use of nasal CPAP by patients.