Patients with type 2 diabetes and obstructive sleep apnoea may not experience improved glycaemic control by using continuous positive airway pressure (CPAP) as some studies have suggested.
The findings from a randomised, controlled trial by researchers in Australia and the US contradict a recent Spanish study.
The authors of the new study randomly assigned 298 patients with “relatively well-controlled” type 2 diabetes and newly diagnosed with sleep apnoea to receive either CPAP or usual care.
In addition to measuring the change in glycaemic control, researchers studied changes in blood pressure, daytime sleepiness and quality of life over six months.
They found no difference between those receiving CPAP and the control group in change in HbA1c at three and six months.
“Clinicians should have a high index of suspicion for its presence when patients experience daytime sleepiness, snoring and resistant hypertension”
However, there was a greater fall in diastolic blood pressure over six months in the CPAP group (-3.5mmHg versus -1.5mmHg) but it was only significant among those who used the intervention for at least four hours a night.
Daytime sleepiness also improved significantly among those using CPAP, said the researchers in the American Journal of Respiratory and Critical Care Medicine.
Meanwhile, quality of life between the two groups was not statistically significant overall as measured by the RAND 36-Item Short Form Health Survey.
The study authors suggested their findings may be explained by sleep apnoea potentially playing a bigger role in the development of diabetes than its control, setting the bar in the study for CPAP adherence – four hours a night – too low or that CPAP may only benefit those with either severe apnoea or poor glycaemic control or both.
Lead study author Jonathan Shaw, associate professor and head of population health at Melbourne’s Baker IDI Heart and Diabetes Institute, said: “Many studies have indicated that obstructive sleep apnoea may contribute towards the development and progression of type 2 diabetes.
“Although we did not find a glycaemic benefit for its treatment, clinicians should have a high index of suspicion for its presence when patients experience daytime sleepiness, snoring and resistant hypertension,” said Dr Shaw.
“Identification and treatment of obstructive sleep apnoea in these patients may lead to clinically meaningful benefits,” he added.