Objectives To study the cardiovascular and metabolic features of obstructive sleep apnea syndrome (OSAS) patients with normal body mass index.

Methods 221 non-obese patients who attended the sleep centre and hypertension centre of People’s hospital of Xinjiagn Uygur Autonomous Region were selected. All subjects underwent polysomonography (PSG) and biochemical tests, the sleep parameters, blood pressure and metabolic features were compared between patients with and without OSAS. Logistic regression model was set up to explore the possible risk factors of OSAS.

Results (1) The mean age, neck circumference, AHI, the duration of oxygen saturation less than 85% were significantly greater in OSAS group (P value<0.05 for all). (2) The mean pulse pressure of day-time, night and the whole day were much higher but the mean heart rate was significantly lower in OSAS patients than those in non-OSAS individuals. (3) LDL-c level was different between OSAS group and non-OSAS group [(2.64 ± 0.77) vs. (2.29 ± 0.74)mmol/L, P = 0.017] adjusting for age, sex, BMI etc. (3) The age and neck circumference were risk factors of non-obese OSAS patients, greater neck circumference may increase 1.20-fold risk (95% CI 1.05-1.38) of OSAS.

Conclusions The pulse pressure and LDL-c level were higher in non-obese patients with OSAS while the heart rate was lower. Aging and greater neck circumference may be risk factors of non-obese OSAS.