This article reports on findings by Dr. Weinstock and others in the May edition of the Journal Sleep. Impaired glucose tolerance (IGT) is a precursor to diabetes. Studies have shown a link between obstructive sleep apnea (OSA) and IGT as well as diabetes. But there are few studies about the effects of treating OSA and the impact on IGT or even diabetes. Dr. Weinstock studied 50 individuals with at least moderate OSA and IGT, but not full blown diabetes. They treated the participants with real CPAP for 2 months and then fake CPAP for two more months. The results showed that in IGT was reduced only in those with severe OSA and obesity. In fact, for every hour of increased CPAP use, there was a significant improvement in glucose tolerance. There was also an effect seen in those with excessive sleepiness, regardless of weight or OSA severity - however there were not enough participants in this category to be statistically significant.
The study authors concluded that for those with obesity and mild to moderate OSA, 8 weeks of CPAP is not helpful in improving glucose tolerance. Eight weeks of CPAP did improve glucose tolerance (although it did not normalize it) in those with severe OSA regardless of obesity. Therefore, it may be helpful to screen patients with IGT for sleep disordered breathing and to especially treat those with severe OSA. This may reduce the chance of those patients going on to develop full blown diabetes. Of course, more studies are needed to demonstrate that effect.