OSA and type-2 diabetes - which is the chicken? Or are they both eggs?

A recent round - table expert discussion published in the journal 'Diabetes, Obesity and Metabolism' (11,2009, 733-741) was clearly based on the International Diabetes Federation report on sleep disordered breathing and type 2 diabetes. Each paper attests to a growing interest in the relationship between these two disorders.

Some of the major points were:

1. There is a diabetes epidemic globally. Interstingly the diabetologists are urging the medical community to pay attention to a related epidemic of obstructive sleep apnoea, and to commit to research into how the two may be linked.

2. Obstructive sleep apnoea, some studies have suggested, may contribute to impaired glucose control. And CPAP therapy may reverse the damage. Unfortunately other studies have contradicted this, and the jury is still out.

3. The association between type 2 diabetes and OSA is independent of obesity. Intermittent hypoxia overnight and sleep fragmentation is thought to set off a 'cascade of events' which may contribute to the development of some of the morbidity associated with OSA. Including diabetes. The language is floridly descriptive, but the details are still sketchy!

4. Whether diabetes causes OSA (perhaps via an autonomic neuropathy) or vice versa (chicken or egg), or whether both are simply markers of the same phenotype (both eggs? both chickens? Now that wouldn't be a very productive metaphorical partnership) is open for debate. 40% of patients with OSA have type 2 diabetes, and up to 23% of patients with type 2 diabetes have OSA. So patients in each population group should be evaluated for the possible coexistence of the other condition

5. How to screen patients with diabetes for OSA is not codified. Furthermore, how to evaluate those felt to be at high risk will depend on the local availability of specialist sleep medicine services. The 'expert panel' round table discussion - sponsored by a CPAP company - felt that any patients with a high Epworth Sleepiness Scale or Berlin Questionnaire score should be evaluated with polysomnography. It is worth asking if they snore, or if there have been witnessed apnoeas - as positive answers to these questions significantly heighten the pre-test probability.

6. Treatment of OSA with CPAP may - or may not - help with diabetes control. Weight loss, however, is a clear winner across the board.

Watch this space. If obstructive sleep apnoea hangs on to the coat tails of type 2 diabetes.....

Andrew