US researchers report that disrupting sleep damages the body's ability to regulate blood sugar levels, potentially raising the risk of developing type 2 diabetes. In an experiment, researchers at the University of Chicago Medical Center found that disrupting the deepest sleep periods of volunteers rapidly resulted in reduction in their ability to regulate blood-sugar levels. Normal sleep is divided into several stages, with the so-called slow-wave sleep considered the deepest. Whenever the volunteers went into slow-wave sleep the researchers made noise - enough to disturb the sleep though not to fully awaken them. After just three days the ability of the volunteers to regulate blood sugar was reduced by 25 per cent, the researchers reported. Earlier studies have indicated that lack of sleep can reduce the ability to regulate sugar, and this report adds evidence that poor sleep quality is also a diabetes risk.