Scientists have discovered that a component of your noctural nap, known as slow wave sleep, is critical to helping the body to regulate sugar levels and stave off diabetes.
Writing in the journal PNAS, Esra Tasali and her colleagues at the University of Chicago Medical Center recruited nine healthy young volunteers and monitored their sleep. The subjects were rigged up to a monitor which played noise from a speaker whenever their brain waves showed that they had entered slow wave sleep, which is the deepest phase of sleep. The sounds were just loud enough to disrupt the subjects' sleep, but without waking them up. This occurred about 250 times during the night for each subject and enabled the researchers to cut the amount of slow wave sleep amongst the volunteers by 90%. The effect is similar to ageing the brain by 40 years, says Tasali. "In this experiment we gave people in their 20s the sleep of someone in their 60s."
When the volunteers woke up each morning the researchers administered a small amount of glucose, intravenously, and then monitored blood sugar and insulin levels. The researchers were surprised to see that by the end of the study the volunteers had become 25% less sensitive to insulin and their glucose levels were 23% higher. The team point out that their findings might help to explain why obese and some elderly individuals develop type II diabetes. Both old age and obesity are associated with poor sleep, which could be responsible, at least in part, for triggering some of the cases of diabetes seen in these individuals.
"Our findings raise the question of whether age-related changes in sleep quality contribute to the development of these metabolic alterations," the team say.