An increased body mass index (BMI) is a risk factor for type 2 diabetes mellitus and obstructive sleep apnoea (OSA). The question whether this is just a shared risk factor or whether there is a deeper relationship has been addressed by West et al¹ who used an initial screening Berlin questionnaire followed by overnight oximetry in selected respondents. OSA was found to be highly prevalent in this patient group. Although BMI was the best predictor of OSA, type 2 diabetes conferred a significant extra increase in the likelihood of having OSA after allowing for BMI, age and neck size.

We have examined the risk of OSA in a district general hospital diabetes clinic. We used the Berlin questionnaire and assessed sleepiness using the Epworth score in 63 people (30 women) with type 2 diabetes and a BMI of >30 kg/m². Diabetic control was assessed using HbA1C. Thirty-five patients (56%, 16 women) were found to have a high risk of OSA.

Despite the suggestion that improvement in sleep-disordered breathing using continuous positive airway pressure improves glucose intolerance in both the short and long term, no significant association was found between poor glycaemic control and the Berlin questionnaire risk group category.^2,3

These results are similar to those of West et al and suggest the potential of a high burden of unrecognised OSA in people with diabetes. Furthermore, our findings are not restricted to the male population. We feel that clinicians who manage patients with type 2 diabetes should have a heightened awareness of the increased likelihood of OSA in this group. The Berlin questionnaire is easy to use and is an attractive alternative in the initial screening for OSA, particularly where access to sleep studies and oximetry is very limited.