Sleep apnoea has been linked with elevated blood sugar levels, suggesting people with the condition could be at an increased risk of cardiovascular illness and mortality.

The findings of a new study, published in the European Respiratory Journal, add to a growing body of evidence that suggests that sleep apnoea is linked with diabetes.

The research analysed 5,294 participants from the multinational European Sleep Apnoea Cohort. The researchers measured levels of HbA1c, which correlates with average plasma glucose concentration. This measurement allows researchers to gain an understanding of blood sugar levels over a period of time.

People with diabetes have higher levels of HbA1c and the risk of developing cardiovascular complications is increased as these levels are raised. (The target levels for HbA1c are 4.0-5.9% for non-diabetics and up to 6.5% for diabetics).

The study was carried out in non-diabetic people to investigate whether HbA1c was linked with sleep apnoea in a group of people with varying levels of glucose concentration.

The results found that levels of glucose concentration were significantly linked with the severity of sleep apnoea. The participants were divided into groups based on their level of sleep apnoea severity and HbA1c levels rose from 5.24% in the group with lowest severity to 5.50% in the group with the highest severity. The findings highlight the need for clinicians to be aware of the risks of diabetes when treating sleep apnoea.

Professor Walter McNicholas, an author of the study, said: "This is the largest study of its kind showing a link between sleep apnoea severity and glucose levels. Clinicians need to focus on diabetes as an important co-existing illness when treating people with sleep apnoea. Further studies are needed to understand the mechanisms behind these two conditions. I would also emphasise to patients the importance of weight control as a way to reduce the risks associated with the condition."