Daytime sleepiness and nasal continuous positive airway pressure therapy in obstructive sleep apnea syndrome patients: effects of chronic treatment and 1-night therapy withdrawal.

A multiple sleep latency test (MSLT) was performed in 30 patients with obstructive sleep apnea syndrome (OSAS) at the time of diagnosis and after 1 year of home therapy with nasal continuous positive airway pressure (nCPAP). The MSLT was administered after two consecutive polysomnographic studies, one with (CPAP) and one without nCPAP (NCPAP) at baseline and at follow-up. After a year of therapy, the MSLT significantly rose from 3.1±0.3 to 9.8±1.0 minutes (p=0.001). The increase in mean sleep latency was significantly correlated with the decrease in the number of arousals during the night (r=-0.48, p=0.009). On the basis of MSLT value at follow-up, patients were split into two subgroups: the normalized group, in which 15 patients had an MSLT≥10 minutes, and the unnormalized group, consisting of 15 patients with an MSLT<10 minutes. Normalized patients differed for a higher apnea+hypopnea index (AHI) time at baseline, a greater improvement in nocturnal hypoxemia and a greater nCPAP use at follow-up. After 1 night of therapy withdrawal, MSLT fell dramatically to 5.3±0.6 minutes, even though the subjects said they did not feel sleepy. The changes in MSLT after the night of treatment suspension were not correlated with changes in body mass index (BMI), AHI or nocturnal hypoxemia, whereas they were correlated negatively with changes in AHI time (r=-0.53, p=0.003) and with the decrease in the number of arousals (r=-0.47, p=0.009). The results of this study suggest: 1) nCPAP therapy reversed the diurnal sleepiness in long-term OSAS patients without a complete normalization. 2) The major improvement in MSLT appeared to be related to greater reported therapy compliance. 3) Interruption of therapy for only 1 night abruptly decreased the objective level of daytime alertness even in the absence of subjective worsening