The effects of continuous positive airway pressure (CPAP) for obstructive sleep apnoea (OSA) on insulin resistance are not clear; trials have found conflicting results and no appropriate control groups have been used.
Methods: Forty two men with known type 2 diabetes and newly diagnosed OSA (>10, >4% SaO2 dips/hour) were randomised to receive therapeutic (n=20) or placebo CPAP (n=22) for 3 months. Baseline tests were performed and repeated after 3 months. The study was double blind.
Results: Results are expressed as mean (SD). CPAP improved the Epworth sleepiness score significantly more in the therapeutic group than the placebo group (-6.6 (4.5) vs. -2.6 (4.9), p=0.01). The maintenance of wakefulness test improved significantly in the therapeutic group, but not in the placebo group (+10.6 (13.9) vs. -4.7 (11.8) mins, p=0.001). Glycaemic control and insulin resistance did not significantly change in either the therapeutic or placebo groups: HbA1c (-0.02 (1.5) vs. +0.1 (0.7), p=0.7, 95% CI -0.6% to +0.9%), euglycaemic clamp (M/I: +1.7 (14.1) vs. -5.7 (14.8), p=0.2, 95% CI -1.8 to +0.3 l/kg/min1000), HOMA-%S (-1.5 (2.3) vs. -1.1 (1.7), p=0.4, 95%CI -0.3 to +0.08%) and adiponectin (-1.1 (1.2) vs. -1.1 (1.3), p=0.2, 95% CI -0.7 to +0.6 ug/ml). Body mass index, bioimpedance and anthropometric measurements were unchanged. Hours of CPAP use per night were: therapeutic 3.6 (2.8) vs. placebo 3.3 (3.0), p=0.8. There was no correlation between CPAP use and the measures of glycaemic control or insulin resistance.
Conclusion: Therapeutic CPAP does not significantly improve measures of glycaemic control or insulin resistance in men with type 2 diabetes and OSA.
- glucose clamp technique