Prevalence and recognition of obstructive sleep apnea in Chinese patients with type 2 diabetes mellitus.
BACKGROUND
Obstructive sleep apnea (OSA) is associated with disorders of glucose metabolism. Previous studies revealed a high prevalence of OSA among subjects with type 2 diabetes mellitus (DM). The aims of this study were to determine the prevalence of OSA and associated clinical factors in Chinese patients with DM.


METHODS
All records of the DM clinic at a teaching hospital in Hong Kong were screened between January 2007 and June 2008. Inclusion criteria for patients were Chinese, aged 18 to 75 years, with type 2 DM. Patients with unstable medical illnesses, gestational diabetes, or on renal replacement therapy were excluded.


RESULTS
Of 3,489 records screened, 1,859 subjects were eligible. A random sample of 663 (mean age, 58.2 ± 10.8; mean BMI, 26.0 ± 4.6), except six with known OSA, were invited for polysomnography (PSG). Of 165 subjects on which PSG was performed, OSA was diagnosed (apnea-hypopnea index [AHI] ≥ 5.0/h) in 89 subjects (53.9%, median Epworth Sleepiness Scale, 6 [interquartile range 3, 10]). Fifty-four (32.7%) had moderate/severe OSA (AHI ≥ 15/h). The estimated OSA prevalence in this diabetic cohort was 17.5% (24.7% in men, 10.3% in women). Regression analysis identified that AHI was associated independently with higher BMI, advanced age, male sex, and higher diastolic BP (R(2) = 29.6%). The adjusted OR of requiring three or more antihypertensive drugs in moderate/severe OSA was 2.48 (95% CI, 1.05-5.87). No association between glycemic control (HbA1c) and sleep was identified.


CONCLUSIONS
In conclusion, OSA is more prevalent in Chinese adults with DM than in the general population. A high index of suspicion for OSA in patients with DM is warranted, because they may not have overt daytime sleepiness.