Naricha Chirakalwasan, Busarakum Teerapraipruk, Lalitha Pereirasamy

Introduction: Our prior investigation found positional sleep apnea accounting for approximately 70% of Asian obstructive sleep apnea patients. We hypothesized that the habitual side sleeping may indicate an obstructive sleep apnea deterring mechanism.

Method: We retrospectively reviewed 542 polysomnographic studies from our sleep laboratory. We included adult patients with respiratory disturbance index ≥ 5 from baseline polysomnography. Habitual sleep position was obtained from the pretest questionnaire. 

Results: Forty-eight percent were noted to be habitual supinesleepers. Most habitual non-supine sleepers were habitual side sleepers with predominantly right-sided preference. Most habitual side sleepers when compared to habitual back sleepers were found to be more female, having higher body mass index, and reported more frequent snoring. We also found the differences in polysomnographic fidings in which lower mean oxygen saturation and higher non-supine respiratory disturbance index were observed in habitual side sleepers as compared to habitual back sleepers. Only female sex was a signifiant predictor for being a habitual side sleeper. Total respiratory disturbance index, age>60, and wake after sleep onset >30 minutes appeared as risk factors for developing cardiovascular-related diseases in habitual side
sleeping obstructive sleep apnea patients.

Conclusion: Slightly more than half of obstructive sleep apnea patients were observed to be habitual side sleepers. In comparison to habitual back sleepers, the habitual side sleepers were observed to be more female, obese, having more snoring, and more severe nocturnal oxygen desaturations. Surprisingly, they appeared to have higher respiratory disturbance index during their assumed obstructive sleep apnea deterring position; the side position, than the habitual back sleepers. This is an important fiding which indicates that early diagnosis and treatment of habitual side sleepers are needed because this group of obstructive sleep apnea patients was observed to have more severe disease and positional therapy may not be effective in this group of patients.