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Apnea linked to diabetes?

Study looks at damage caused by interrupted sleep

Study looks at damage caused by interrupted sleep

May 22, 2006|by KRISTIN WILSON

People diagnosed with sleep apnea go to bed knowing that they might stop breathing dozens if not hundreds of times throughout the night.

Their condition can leave them feeling tired or irritable in the morning and increase their risk of developing high blood pressure and heart disease.

As if that wasn't enough to worry about, doctors and researchers in Baltimore and Hagerstown are investigating the link between interrupted sleep conditions such as sleep apnea and a greater susceptibility to developing diabetes.

Doctors started suspecting the link between both conditions while studying participants in Washington County who are part of the ongoing Sleep Heart Health study. Doctors noticed that people with sleep apnea seemed to be more susceptible to diabetes or prediabetes.

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Through the new study called SOMNOS, researchers hope that they will better understand diabetes by better understanding how sleep - or lack of sleep - affects metabolism.

"We are starting to learn that sleep is no longer a luxury," says Dr. Naresh Punjabi, principal investigator of the SOMNOS study. "We used to think of sleep as a passive state, but it turns out that it is a very complex process that is very, very important to biological functions."

During the past decade, doctors have learned through research that getting adequate sleep is not just about feeling refreshed in the morning. Research shows that regulatory body functions like hormone secretion and metabolism control happen predominantly during sleep.

Doctors know that a lack of sleep can negatively impact body functions. But what about the quality of sleep? What happens to the body when someone is roused from a normal sleep pattern multiple times during the night?

A research team at Johns Hopkins University's Hagers-town field center is trying to answer those questions in a series of studies. The SOMNOS study, Sleep Obesity and Metabolism in Normal and Overweight Subjects, is following volunteers both with and without sleep apnea to see how their bodies handle glucose and insulin, explains Melissa Minotti, a registered sleep technician and coordinator of the SOMNOS study.

They are involving people of all ages, all weights and many different health conditions, looking at the relationship between weight, how someone sleeps and the ability to metabolize glucose and insulin.

Two more studies being conducted at the Johns Hopkins Bayview Medical Center in Baltimore isolate the two principal factors of sleep apnea: oxygen deprivation and interruption of sleep.

A study of sleep fragmentation and metabolism takes normal, healthy, young adults and watches what happens when their normal sleeping pattern is continuously interrupted throughout a regular night of sleep. The sleep hypoxia study also uses healthy, young adults but looks only at the biological impact when a person sleeps under oxygen-deprivation conditions. Patients breathe thin air replicating the reduced air flow that people with sleep apnea get.

While all studies are in the early stages, preliminary data suggests that metabolism is negatively affected "when the quality of sleep is bad," Punjabi says.

There is an immediacy to understanding how sleep apnea might trigger diabetic conditions.

Diabetes is one of America's fastest growing disorders, affecting more than 20 million Americans, according to the American Diabetes Association. Sleep apnea is also an increasingly common condition since it is closely related to being overweight or obese.

The National Institutes of Health estimate that about 12 million Americans have been diagnosed with sleep apnea, but Punjabi suspects that the number of people with sleep apnea is much higher since the condition is underdiagnosed.

Edward Grandi, executive director of the American Sleep Apnea Association, says he uses the estimation of 18 million Americans with sleep apnea, although "my sense is there could be as many people who have sleep apnea as have diabetes," he says.

Looking into the effect sleep apnea could have on a person's ability to regulate glucose is a link that makes sense, Grandi says.

"Sleep apnea is not just an annoyance," he says. "It has consequences that affect the entire body."

Prior research has documented the development of high blood pressure, cardiovascular disease and weight gain associated with sleep apnea, Grandi says.

Grandi hopes that more awareness of the serious complications associated with sleep apnea will encourage more people to be tested for the sleeping disorder.

"If you think you have sleep apnea, talk to your physician and get a referral to a sleep lab and go through the study," he says. "If someone is susceptible to sleep apnea, if you dealt with those things now, you can prevent a lot of things from happening in the future."

When someone with sleep apnea falls asleep, the soft tissue in the back of the throat becomes so relaxed that it collapses, closing off the airway. Sleep apnea patients can stop breathing for up to a minute, before the brain wakes up enough to trigger labored breathing. While most sleep apnea patients never fully wake up during the night, their continuously interrupted sleep pattern can make them feel as if they haven't slept enough.

Sleep apnea is treatable, Grandi says. Depending on the severity of the apnea, various treatments are available.

As the SOMNOS study moves forward, continuing to look at the relationship between fragmented sleep and diabetes, Punjabi hopes the research will help doctors catch glucose intolerance earlier that could curb or delay the onset of diabetes. He also hopes the study will further underscore the message of how important it is to get a good night's sleep.

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