Study objectives: The positional dependency of obstructive sleep apnea (OSA) is well known, but objective evidence for the positional effect on snoring is lacking. The aim of this study is to elucidate the effect of body position on snoring, and that of sleep stage as well.

Design: Retrospective analysis of the effects of body position and sleep stage on snoring in nonapneic snorers (snorer group) and OSA patients (apneic group).

Setting: A sleep laboratory in a national hospital in Japan.

Patients: Seventy-two patients who complained of habitual snoring and underwent overnight polysomnography.

Interventions: N/A.

Measurements and results: In the lateral position, most subjects in the snorer group showed decreased snoring both in time (p = 0.0004) and intensity (p = 0.0003), but subjects in the apneic group showed variable changes. In the apneic group, the positional dependency of snoring (the ratio of lateral value to supine value) was correlated with supine apnea-hypopnea index (AHI), that is, OSA patients with higher supine AHI tended to show increased snoring in the lateral position. AS to the effect of sleep stage, snoring was increased in deeper non-rapid eye movement sleep and decreased in rapid eye movement sleep in a given position.

Conclusions: This study demonstrated that the positional dependency is different between nonapneic snorers and OSA patients. Most of the nonapneic snorers snore less in the lateral position than in the supine position in contrast to OSA patients who often fail to decrease snoring even in the lateral position.