The relationship between subjective sleepiness and polysomnographic findings in sleep apnea syndrome

: We investigated factors of daytime sleepiness in 22 middle-aged male patients with sleep apnea syndrome (SAS) using the Epworth sleepiness scale (ESS) and polysomnography. The subjects were classified into two groups according to ESS score as follows; low ESS group: ESS score or = 10. ESS score was significantly correlated with duration in which nocturnal oxygen saturation decreased below 90% (Time of SpO2 < 90%) (r = 0.54, p < 0.05). Time of SpO2 < 90% and percent of movement arousals at the termination of apnea/hypopnea (number of movement arousal/total number of apnea/hypopneas x 100) were significantly higher in high ESS group than in low ESS group. Our findings suggest that the severity of oxygen desaturation and sleep fragmentation caused by arousal response at the termination of apnea/hypopnea may be important factors of daytime sleepiness in patients with SAS.