Obstructive sleep apnoea and type 2 diabetes

Aims: To establish the prevalence of OSA in individuals with type 2 diabetes, and whether treatment with CPAP improves glycaemic control and insulin resistance. Methods and Results: A questionnaire was sent to 1682 men with type 2 diabetes from hospital and primary care databases. Fifty-six percent replied; 57% scored as 'high' and 39% as 'low' risk for OSA; 4% had known OSA. Overnight oximetry in 240 respondents from the 'high' and 'low' risk groups showed 31% and 13% respectively had significant OSA, verified by sleep studies. Exploration and oximetry data to the questionnaire respondent population suggests 23% have OSA. Comparison with a general population showed OSA prevalence to be significantly higher in the diabetes population (p<0.001). Multiple linear regression revealed diabetes was a significant independent OSA predictor after correction for BMI, explaining 8% of OSA variance (p<0.001). There was no correlation of OSA with HbA1c. A double blind randomized controlled trial of CPAP in men with type 2 diabetes and newly diagnosed OSA was performed. Forty-two men attended for baseline investigations and then received either therapeutic or placebo CPAP for 3 months; baseline tests were then repeated. In the therapeutic group, significantly improved subjective and objective sleepiness were noted, however no significant improvement in HbA1c, euglycaemic clamp, adiponectin or HOMA-%S were found. Conclusions: OSA is highly prevalent in men with type 2 diabetes; most individuals are undiagnosed. Diabetes may be a significant independent contributor to OSA risk. CPAP treatment of OSA does not improve insulin resistance or HbA1c in men with type 2 diabetes.