Positive airway pressure does not improve glycaemic control in people with type 2 diabetes and obstructive sleep apnoea, an Australian led study shows.

However the randomised study published in the American Journal of Respiratory and Critical Care Medicine found the treatment had other benefits including reduced daytime sleepiness and a small reduction in blood pressure.

Associate Professor Jonathan Shaw, head of population health research at the Baker IDI Heart and Diabetes Institute, and colleagues screened patients without a previous diagnosis of OSA attending specialist diabetes clinics.

They randomised a total of 298 patients who were found to have the disorder, and an HbA1c of 6.5-8.5%, to PAP or usual care.

Six months later there was no difference between the groups in HbA1c, even among those with worse glycaemic control at baseline, more severe OSA or better adherence to PAP treatment.

PAP did, however, reduce diastolic blood pressure by 3.5 mmHg compared to a drop of 1.5 mmHg in the control group.

Active treatment also reduced sleepiness and improved measures of vitality and mental health assessed in a quality of life scale.

“Our findings argue against routine screening for OSA in all people with type 2 diabetes,” Professor Shaw told the limbic.

“But since OSA is common in people with type 2 diabetes, clinicians should have a high index of suspicion for its presence based on clinical indicators such as daytime sleepiness, snoring and resistant hypertension.”

Identification and treatment of OSA in these settings may lead to meaningful clinical benefits despite no effect on glycaemic control, he said.

The research team noted that the findings applied to a relatively narrow group of patients with reasonably good glycaemic control and no prior diagnosis of OSA.

“It may be that OSA treatment would only succeed in improving glycaemic control in patients with a combination of relatively severe OSA and poor glucose levels, and in whom adherence to CPAP is high,” Professor Shaw said.

“However, this hypothesis would need testing in a separate study.”