Study Objectives: Subjectively assessed snoring and sleepiness are known to be related. However, no evidence supporting the usefulness of snoring measurements exists. We examined whether the objectively measured snoring intensity was correlated with sleepiness. Methods: The records of 515 patients who underwent polysomnography for suspected obstructive sleep apnea were retrospectively reviewed. Subjective sleepiness was assessed using the Epworth sleepiness scale (ESS). Snoring intensity was assessed using the highest one percentile ambient sound pressure level (L1) attained while asleep during polysomnography. Results: L1 was correlated with ESS in apneic patients with an apnea-hypopnea index (AHI) ≥15 (r = 0.38, p < 0.0001), but not in other patients. The correlation in the apneic patients was preserved after adjustments for various confounding factors, including the AHI. A step-wise multiple regression in the apneic patients adopted desaturation time, L1, daily sleep time, subjective snoring, and nasal obstruction symptoms as determinants for the ESS. L1 was correlated with the mean pulse rate during polysomnography but not with sleep fragmentation variables after adjustment for the AHI. Conclusions: The measured snoring intensity was independently related to sleepiness in apneics. Snoring intensity may explain part of sleepiness that cannot be fully explained by ordinary polysomnographic variables.
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