Impact of CPAP treatment on HbA1c in patients with severe obstructive sleep apnea and type 2 diabetes mellitus

Abstract

Introduction There is increasing prevalence of obstructive sleep apnea (OSA) in patients with type 2 diabetes mellitus. The causal role of obstructive sleep apnea in this association has not been well delineated. Objectives To investigate the effect of CPAP on HbA1C and cardiometabolic profile in diabetic patients with OSA. Methods In this randomized controlled study, patients were recruited from diabetic clinic in a tertiary university teaching hospital for inlaboratory polysomnography. Those patients with an apnea hypopnea index (AHI) ≥ 15 were randomly assigned to either CPAP or control group for 3 months of treatment. Epworth sleepiness scale, anthropometric and blood pressure measurements, and urinary microalbumin were collected. Fasting blood was taken for insulin, glucose, lipid and glycated haemoglobin levels. Endothelial function was assessed by EndoPAT. Results 64 diabetic patients were recruited, 32 were assigned to each group (CPAP and control), with a mean (±SD) age of 55±9 years, BMI of 30.9±6.5 kg/m2, HbA1C of 8.1±1.2% and AHI of 47.3±23.6. There were no differences of clinical parameters between two groups at baseline. After 3 months of CPAP treatment, there were significant decreases in systolic blood pressure (144 to 134 mmHg; 95% CI, 4.4 to 16.8; p=0.001), diastolic blood pressure (83 to 77 mmHg; 95%CI, 1.8 to 10.5;p=0.007); HbA1C (8.0 to 7.7%, 95%CI, 0.01 to 0.6;p=0.041); and serum triglycerides (1.9 to 1.5 mmol/L;95%CI, 0.22 to 0.58;p<0.001) in the CPAP group while no changes were seen in the control group. When we compared CPAP group with the controls, there was significant reduction in systolic blood pressure (9.1 mmHg; 95%CI, 0.3 to 17.9; p=0.044), HbA1C (0.5%;95%CI, 0.1 to 0.8;p=0.023), and serum triglycerides (0.3 mmol/L;95%CI, 0.02 to 0.5;p=0.035). Conclusions 3 months of CPAP treatment improves glycemic control and the metabolic profile in patients with severe OSA and type 2 diabetes mellitus.