20/20: Sleep Debt

March 30 -- Tens of millions of Americans suffer from a condition that until recently, most health professionals did not take seriously. It can accelerate the aging process, lead to obesity and increase the risk of some diseases. It's garden-variety sleep deprivation and it might be more of a problem than you think.

For the first time, scientists are looking seriously at what happens to our bodies when we live on five, six or seven hours of sleep a night and what they're finding is shocking.

Upsets Blood Sugar

Dr. Eve Van Cauter is a sleep science trailblazer whose research team at the University of Chicago recently published the first study to specifically examine the physical health impact of ordinary sleep deprivation. She calls the impact of sleep debt on the body, "astonishing."

After four hours of sleep for six consecutive nights, healthy young men had blood test results that nearly matched those of diabetics. Their ability to process blood sugar was reduced by 30 percent, they had a huge drop in their insulin response, and they had elevated levels of a stress hormone called cortisol, which can lead to hypertension and memory impairment.

"We had results that were more compatible with individuals 60-years-old than with young, fit men in their early '20s," Van Cauter explains.

Perhaps equally incredible is that until Van Cauter's study, most scientists believed that sleep debt did not cause any significant physical problems. "The concept that sleep is for the mind not the body prevailed and so no one was really looking at the possibility that sleep loss has an impact on health,"Van Cauter says.

Though subjects in the study slept only four hours a night, Van Cauter says sleeping six or seven hours might be just as dangerous. "Six hours instead of four hours, would have a similar impact but would just take a longer period of time," she says.

After the experiment, the six men could make up for their sleep debt. It is unclear, however, how sleep debt affects the body over long periods of time. Van Cauter's early findings suggest that chronic short sleepers have a hard time keeping their blood sugars stable, which makes them prone to insulin resistance and obesity. Experts are now speculating that lack of sleep could be the missing link in understanding America's obesity epidemic.