Polysomnographic Parameters Related to Daytime Sleepiness in Obstructive Sleep Apnea Syndrome: A Preliminary Study

Abstract

Background and Objective Daytime sleepiness is frequently observed in patients with obstructive sleep apnea syndrome (OSAS). The aim of the present study is to assess the parameters that are related to daytime sleepiness in OSAS. Methods We included patients with OSAS who underwent overnight polysomnography (PSG) followed by a next-day multiple sleep latency test (MSLT) and Epworth Sleepiness Scale (ESS) measurement. The respiratory disturbance index (RDI) was used for diagnosis and assessment of the disease severity. Results A total of 34 patients were evaluated, among whom 85.3% were male and the other 14.7% female. The mean value of the mean sleep latency (MSL) in the MSLT was 6.27 ± 3.67 minutes (range 1.70–13.40, median 5). We divided patients into two groups according to their median MSL value. The sleepier group exhibited a higher body-mass index (BMI; 27.04 ± 4.20 versus 24.59 ± 2.12), shorter rapid eye movement (REM) sleep latency (80.21 ± 28.61 min. versus 119.44 ± 55.91 min.), greater sleep efficiency (88.82 ± 6.37% versus 82.43 ± 10.43%), and higher respiratory event-related arousal index scores (RERAI; 3.92 ± 2.3/h versus 2.4 ± 1.85/h) than the less sleepy group. RDIs, apnea/hypopnea indices and oxygen saturations did not differ between the groups. Total ESS scores were also not different significantly. Conclusions A higher BMI, shorter REM latency, relatively higher sleep efficiency and a higher RERAI in the PSG were related to shorter MSL in the MSLT and thus daytime sleepiness in OSAS patients.

Keywords

• Daytime sleepiness
• Obstructive sleep apnea syndrome
• Epworth sleepiness scale
• Multiple sleep latency test
• Polysomnography