Impact of gender and sleep position on relationships between anthropometric parameters and obstructive sleep apnea syndrome

Objective: Considering the mechanisms by which obesity affects obstructive sleep apnea syndrome (OSAS) and the differences of fat distribution depending on gender, associations between anthropometric parameters, and OSAS may differ depending on gender or sleep position. We analyzed the impact of gender and sleep position on the relationship between fat distribution and development of OSAS. Methods: One thousand thirty-two consecutive subjects were analyzed. Recorded anthropometric measurements and overnight polysomnographic data of the subjects were reviewed retrospectively. The presence of OSAS was defined by the respiratory disturbance index (RDI) ≥5 with documented symptoms of excessive daytime sleepiness. Results: Eight hundred fifty-eight males and 174 females were included. Male subjects had significantly higher body mass index (BMI), larger waist circumference (WC), and lower percent of overall body fat (P < 0.0001, P < 0.0001, and P < 0.0001, respectively). The severity of OSAS was significantly higher in male subjects (RDI 26.9 ± 22.4 in males vs. 10.2 ± 13.8 in females, P < 0.0001). In male subjects, BMI, WC, and overall body fat were significantly associated with severity of OSAS and had larger impacts on supine RDI than lateral RDI. Overall body fat was not associated with severity of OSAS in female subjects, and there were no significant differences of the associations between all anthropometric parameters and RDIs depending on sleep position. Conclusions: Evaluation of the correlation of anthropometric data with severity of OSAS should consider sleep position as well as gender.