People with sleep apnea — disordered breathing while they slumber — are more likely to develop cancer or to die from it than people with no breathing problems, two new studies suggest.
Those who had severe sleep apnea were found to be nearly five times more likely to die from cancer over the 22-year period of one of the studies.
In the other study, people with apnea had an increased risk of developing any type of cancer, and those with the most severe apnea had the greatest risk.
The new findings seem to agree with studies in animals that show tumor growth is promoted by an inadequate supply of oxygen.
The studies found only an association — they do not suggest sleep apnea causes cancer or contributes to its growth, the researchers said. But if future studies confirm the results, diagnosis and treatment of sleep apnea in patients with cancer might prolong their survival, said study researcher F. Javier Nieto, of the University of Wisconsin-Madison School of Medicine and Public Health.
The studies were presented this week at an American Thoracic Society meeting in San Francisco.
Previous studies have linked sleep apnea with increased risks of high blood pressure, heart disease, depression, and early death from any cause. The condition is characterized by pauses in breathing or shallow breathes during sleep, according to the National Institutes of Health. Such pauses can last for seconds to minutes, and often occur five to 30 times or more an hour. At least 1 in 10 people older than 65 has sleep apnea, the NIH says.
In the study of cancer mortality rates, Nieto and colleagues analyzed information from 1,522 Wisconsin residents who enrolled in a sleep study in 1989. Every four years, the participants underwent a polysomnography test — an all-night recording of their sleep and breathing — along with other medical tests.
The worse the participants' sleep apnea was, the more likely they were to die from cancer during the 22-year study period, the researchers said. Participants with severe sleep apnea were 4.8 times more likely to die than those with sleep breathing problems. The link was stronger among non-obese people than obese people.
The results held even after the researchers took into account factors that could affect a person's risk of death from cancer, including age, sex, body mass index (BMI) and smoking.
In the other study, researchers in Spain gathered data on 5,246 patients who were diagnosed with sleep apnea in seven Spanish hospitals between 2000 and 2007, and found that 5.7 percent of them developed some type of cancer during the study period.
In a separate study, also presented at the meeting, researchers from Spain found that the link between an inadequate supply of oxygen and increased cancer growth was stronger in lean mice than in obese mice.
Pass it on: Two new studies associate cancer with sleep apnea.