Effect of one week of CPAP treatment of obstructive sleep apnoea on 24-hour profiles of glucose, insulin and counter-regulatory hormones in type 2 diabetes

Studies examining the impact of CPAP treatment on glycaemic control have yielded conflicting results, partly because of insufficient nightly CPAP use. We examined the 24-hour profiles of glucose, insulin and counter-regulatory hormones in 12 subjects with type 2 diabetes and OSA before and after 1 week of effective in-laboratory CPAP therapy over an entire 8-hour night thus ensuring optimal CPAP compliance. Blood samples were collected every 15 to 30 minutes for 24 hours under controlled conditions. The 24-hour mean glucose decreased from 153.2 +/- 33.0 to 139.7 +/- 24.2 mg/dL with CPAP (-13.5 +/- 13.5 mg/dL; P =.005) without change in insulin levels. Morning fasting glucose levels decreased by 14.6 +/- 3 mg/dL (P =.001) and the dawn phenomenon decreased by 7.8 +/- 9.8 mg/dL (P =.019). CPAP treatment decreased norepinephrine levels while the 24-hour profiles of growth hormone and cortisol remained unchanged. In conclusion, 1 week of effective treatment of OSA over an entire 8-hour night results in a clinically significant improvement in glycaemic control via an amelioration of evening fasting glucose metabolism and a reduction in the dawn phenomenon, a late-night glucose increase that is not adequately treated by oral medications. Clinical Trials Information: ClinicalTrials. gov Identifier: NCT01136785.