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The prevalence of syndrome Z (the interaction of obstructive sleep apnoea with the metabolic syndrome) in a teaching hospital in Singapore

¹ Department of Medicine, Changi General Hospital, Singapore
² Changi General Hospital, Singapore

Correspondence to:
Correspondence to:
Dr Sridhar Venkateswaran
Department of Medicine, Changi General Hospital, 2 Simei Street 3, Singapore 529889; sridhar_venkateswaran{at}cgh.com.sg

Background: Syndrome Z describes the interaction of obstructive sleep apnoea (OSA) with the metabolic syndrome.

Purpose of study: A pilot study to determine the prevalence of syndrome Z in a teaching hospital in Singapore.

Methods: Patients (age 18 years) recruited for this prospective study had to satisfy three of the following five inclusion criteria: fasting glucose >6.1 mmol/l, blood pressure 130/85 mm Hg, HDL cholesterol <1.04 mmol/l in men and <1.2 mmol/l in women, triglycerides 1.7 mmol/l, and a waist circumference >102 cm in men and >88 cm in women. All subjects underwent standard overnight polysomnography. Overnight fasting glucose and lipid levels were measured and baseline anthropometric data recorded. All sleep studies were scored and reported by a sleep physician. OSA was deemed to be present if the respiratory disturbance index (RDI) was 5, with mild, moderate and severe categories classified according to the Chicago criteria.

Results: There were 24 patients (19 males and five females) of whom 10 were Chinese, eight Malay and five of Indian origin, with one other. Mean age was 48±13.5 years, mean body mass index was 34.9±6.1 kg/m² and mean waist circumference was 111.3±15.7 cm. 23 (95.8%) of the patients had OSA with a mean RDI of 39.6±22.4 events/h with 15 patients (62.5%) in the severe category. The five patients who fulfilled all five criteria for diagnosis of the metabolic syndrome had severe OSA.

Conclusion: The prevalence of OSA in our studied population exhibiting the metabolic syndrome is very high. Therefore, a polysomnogram should always be considered for this subset of patients.

Abbreviations: BMI, body mass index; NCEP, National Cholesterol Education Program; OSA, obstructive sleep apnoea; RDI, respiratory disturbance index

Keywords: glucose; pilot study; polysomnography; prevalence; sleep