Obstructive sleep apnoea is associated with risk factors comprising the metabolic syndrome

Background and objective: Several features of OSA syndrome suggest that it is a manifestation of the metabolic syndrome (MS). In this study, we investigated the prevalence of the MS among male Japanese patients with OSA, as well as the relationship between OSA in non-obese patients and components of the MS other than obesity (hypertension, dyslipidaemia and glucose intolerance). Methods: The study included 416 Japanese men who were diagnosed as having OSA by polysomnography. Among these, 101 non-obese patients were selected and the severity of OSA, as well as the prevalence of hypertension, dyslipidaemia and glucose intolerance, was assessed. Results: The MS was associated with OSA in 218/416 patients (52.4%). A significant increase in the prevalence of the MS was associated with increased severity of OSA, as categorized according to AHI. In the non-obese patients with OSA (mean age 57.6 years, BMI 22.7 kg/m(2), AHI 34.3 events/h), hypertension, dyslipidaemia and glucose intolerance were identified in 70 (69.3%), 43 (42.6%) and 20 patients (19.8%), respectively. At least two of these factors were identified in 40 patients (39.6%). Non-obese patients with severe OSA had a significantly higher prevalence of two or more of these factors (33/59 patients, 55.9%). Conclusions: Although Asians are generally less obese than Caucasians, the prevalence of the MS was high among Japanese patients with OSA, and even among non-obese patients, OSA was associated with risk factors for the MS.