Determinants of MSLT- defined sleepiness in OSA patients with neuropsycological findings

Obstructive sleep apnea (OSA) is a common breathing disease charecterized by excessive daytime sleepiness (EDS) as a main symptom. Our aim in this study was to identify the determinants of EDS detected by multiple sleep latency test (MSLT) in OSA patients and to investigate its relationship with neuropsycological functions.

In this prospective study, for a3 months period all participants underwent overnight polysomnography (PSG) followed by MSLT, conducted according to American Academy of Sleep Medicine (AASM) guidelines. EDS was defined as MSLT score < 8 min, while severe EDS was considered as < 5 min. Neurocognitive function and depressive symptoms were assessed using questionaires.

A total of 82 patients (mean age: 50.1 ± 14 years, 34 females, 41.5%) were included. The minumum oxygen value and oxygen desaturation index (ODI) were detected as the main indicators of MSLT-linked EDS in multivariate analysis. It was determined that each increase in ODI value increased EDS by 1.03 times, while an increase in oxygen level caused a 0.89-fold decrease in EDS. According to the Mini Mental Test (MMT) and Beck Depresion Inventory (BDI) results, a total of 33 (40.2%) of the patients had mild, 7 (8.5%) had moderate neurocognitive disfunctions and 30 (38%) had depression with no relationship with MSLT-linked EDS when threshold of 8 min was used. However, in the severely sleepy group, the MMT score began to show a significant decline.

EDS was more stroıngly associated with hypoxic burden than with Apnea hypopnea index (AHI). Although neurocognitive impairement and depression was high in OSA, this was relevant only with severely sleepy group.