by Roni Rabin

'Get some sleep." How many times have we ignored that bit of advice?

Sleep, like oxygen, is underrated. Thoroughly abused, taken for granted, sleep is last on our list of priorities - if it even makes the list.

We may be missing more than we realize.

New research suggests sleep may be integral to the way the body resets its biological clocks, enabling it to clean house and regulate metabolism. It may be our ingrained rehab therapy, holistic homespun medicine for body and mind.

A study published last week took a dozen healthy, fit young male volunteers and restricted them to four hours of sleep a night. The deprivation wreaked havoc on the hormones that regulated their appetite and eating. Their levels of ghrelin, a hormone that stimulates appetite, shot up, while levels of leptin, which signals satiety, dropped. And they were hungry.

University of Chicago researcher Eve Van Cauter, who did the appetite study, earlier had found that sleep deprivation left healthy volunteers with increased levels of cortisol, the stress hormone, and impaired glucose tolerance - which can lead to diabetes.

"After six days of four hours of sleep a night, they had a change in glucose tolerance so they were nearly in a pre-diabetic state," Van Cauter said. "We did not expect to see a change of that magnitude."

That's a pretty serious impact, she said, though it was completely reversible.

The findings have ripple implications. It's been known for some time that people who suffer from obstructive sleep apnea are more likely to develop high blood pressure, which puts them at risk of heart disease. The sleep disorder appears to cause changes in the endothelium, tissue that lines the walls of blood vessels and may contribute to narrowing of the arteries. It strains the right side of the heart and, left untreated, can lead to heart failure.

"We've spent years proving the relationship, but we now know there is a definite relationship between sleep apnea and hypertension and have increasing evidence it affects the cardiovascular system in other ways," said Dr. Michael Thorpy, director of the Sleep Wake Disorders Center at Montefiore Medical Center in the Bronx.

Obstructive sleep apnea appears to place patients at heightened risk for a wide array of serious health problems, including strokes, coronary heart disease and cardiac arrhythmias resulting from increased cardiac stimulation.

But sleep apnea - a disorder marked by heavy snoring and gasping for breath, which causes people to stop breathing while they're asleep - tends to afflict people who are overweight or obese. They're already at risk for high blood pressure and metabolic syndromes triggered by excess weight. So it was never clear whether the association be- tween apnea and the medical conditions was causative or not. In other words, which came first: the chicken or the egg?

And sleep apnea does more than just deprive people of sleep: It also causes fragmented sleep and hypoxia, lack of oxygen. That's why Van Cauter's study is significant.

"Our study was looking at people who were young, healthy and fit, so it is only the reduction of the sleep period that brought about these changes," she said.

"So there's no question about the chicken or the egg: Here we are showing the direction - that sleep deprivation can trigger an alteration of appetite regulation, as well as glucose intolerance."

Which makes you wonder whether we take seriously enough the fact that most adults aren't getting enough sleep. According to the National Sleep Foundation, a third of American adults sleep

6 1/2 hours or less a night, and 45 percent say they'll willingly sleep less in order to get more done.

Meanwhile, more Americans are overweight than ever before, and diabetes is on the rise.

Sleep deprivation takes a toll, even on bravado types who seem to function just fine, Van Cauter said. "The person who doesn't feel very tired with sleep restriction is not necessarily the person who has the least changes in biological parameters. You may very well think you can tolerate short sleep, but your biology is very affected."

Neurologist Bradley Vaughn, chief of the sleep and epilepsy division at the University of North Carolina School of Medicine, said he found this when participating in a study of traffic accidents in North Carolina a few years ago. Drivers who fell asleep at the wheel were more likely to have had slept six hours or less the night before, and almost half said they had no idea they were sleepy before the accidents occurred.

Vaughn has treated sleep apnea in patients with epilepsy and says the treatment reduced the frequency and occurrence of seizures by half.

Van Cauter's take is that sleep has an impact on every single bodily system.

"So far, everything - everything - we measured in subjects in whom we restricted sleep was changed," Van Cauter said. "My interpretation is that sleep really affects everything in the body, and we are not wired biologically for sleep deprivation. We're the only animal that does this."

So go ahead: Get some sleep.

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