We've known for some time that obstructive sleep apnea (OSA) is associated with a number of serious health problems, including cardiovascular disease and diabetes. Now, for the first time, two separate studies have found a link between sleep apnea and cancer in humans. This news made big headlines recently -- with good reason.
The results of these studies were both presented recently at an American Thoracic Society conference. These two studies are the first to establish a link between OSA and cancer in humans. Previous studies have shown evidence of a relationship between cancer and sleep apnea in mice.
In one study, conducted at the University of Wisconsin School of Public Health and Medicine, researchers used data from a long-term, extensive sleep study to investigate a possible relationship between obstructive sleep apnea and cancer deaths. The Wisconsin Sleep Cohort Study has compiled 22 years of data on sleep and health for 1,522 men and women, including periodic overnight sleep analysis using polysomnography, a measurement of sleep and breathing. Researchers made adjustments to their analysis to account for other factors that could affect cancer risk, including age, gender, weight, and smoking. Among the participants in the Sleep Cohort Study, researchers found:
• The presence of mild sleep apnea was associated with a 10 percent increase in death from cancer.
• Moderate sleep apnea was associated with a doubling of the risk of cancer death.
• Severe sleep apnea was associated with a nearly five-fold increase in death from cancer.
In the second study, conducted at the Hospital General de Requena in Valencia, Spain, researchers analyzed data from 5,246 patients who where treated for possible sleep apnea between the years 2000-2007. The researchers also adjusted for other genetic and lifestyle factors that influence cancer risk. They found that severe OSA was associated with a 65 percent higher risk of developing cancer.
These two studies mark the first time that sleep apnea and cancer have been linked in humans. But previous studies have found this link in animals. Researchers at the University of Barcelona investigated the link between OSA and cancer in mice. They found what when mice with melanoma were deprived of oxygen periodically, their melanoma tumors grew more quickly than mice that were not deprived of oxygen.
This kind of periodic oxygen deprivation -- known as hypoxia -- is the fundamental characteristic of obstructive sleep apnea. When a person has OSA, his or her airway collapses during sleep, depriving the body of oxygen for a short period of time. Breathing is interrupted, and the levels of oxygen in the blood drop. The severity of sleep apnea is determined by how frequently these periods of interrupted breathing occur. Mild sleep apnea is generally regarded as 5-15 breathing interruptions per hour of sleep, while moderate sleep apnea is measured at 15-30 interruptions per hour of sleep. Severe sleep apnea is considered anything over 30 periods of interrupted breathing per hour of sleep.
It is important to note that neither study established sleep apnea as a direct cause of developing cancer or dying from cancer. What each of these studies did is establish an association between the presence and severity of sleep apnea, and the risk of both developing and dying from cancer. These studies represent an important breakthrough in our understanding of the effects of sleep apnea and oxygen deprivation during sleep. They are a significant first step, and additional research will -- and should -- undoubtedly follow.
These studies also contribute to the growing body of knowledge that sleep apnea, left untreated, is dangerous and damaging to health. Before this latest cancer news, sleep apnea was already associated with several serious health problems, including:
Stroke: One study found sleep apnea present in 91 percent of stroke patients who were evaluated for the sleep disorder.
Heart disease: We've known for some time about a strong association between sleep apnea and heart problems. Sleep apnea is common among patients with high blood pressure, atrial fibrillation, and heart disease. In one study, men with severe obstructive sleep apnea were 68 percent more likely to develop coronary disease and 58 percent more likely to develop heart failure than men without OSA.
Diabetes: A new study found that low oxygen levels in the blood -- a result of OSA -- are associated with elevated blood sugar, and that sleep apnea is a predictor for Type 2 diabetes.
More than 18 million Americans suffer from obstructive sleep apnea, according to the National Sleep Foundation. Many more are likely undiagnosed and therefore going without important treatment. What's more: Sleep apnea and sleep disordered breathing don't just affect adults. Children also are at risk for this sleep disorder and the other health risks that come with it.
Do you need a better reason to pay attention to your sleep, and your family's sleep?
Michael J. Breus, PhD
The Sleep Doctor™
Everything you do, you do better with a good night's sleep™
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