Sleep Apnea Associated with Higher Mortality from Cancer
Madison, Wisconsin, and San Francisco - Sleep-disordered breathing (SDB), commonly known as sleep apnea, is associated with an increased risk of cancer mortality, according to a new study.
While previous studies have associated SDB with increased risks of hypertension, cardiovascular disease, depression, and early death, this is the first human study to link apnea with higher rate of cancer mortality.
Lead author Dr. F. Javier Nieto, chair of the Department of Population Health Sciences at the University of Wisconsin School of Medicine and Public Health, says the study showed a nearly five times higher incidence of cancer deaths in patients with severe SDB compared to those without the disorder, a result that echoes previous findings in animal studies.
"Clearly, there is a correlation, and we are a long way from proving that sleep apnea causes cancer or contributes to its growth," says Nieto, an expert in sleep epidemiology. "But animal studies have shown that the intermittent hypoxia (an inadequate supply of oxygen) that characterizes sleep apnea promotes angiogenesis-increased vascular growth - and tumor growth. Our results suggest that SDB is also associated with an increased risk of cancer mortality in humans."
Dr. Nieto presented his study May 20 at the American Thoracic Society 2012 International Conference in San Francisco. The study was supported, in part, by the National Institutes of Health's the National Heart, Lung, and Blood Institute (NHLBI), the National Institute on Aging, and the former National Center for Research Resources.
|Video: Watch an ABC News report about the sleep apnea study.|
"These findings provide clues to help further our understanding of the relationship between sleep and health," said Dr. Susan B. Shurin, acting director of the National Heart, Lung, and Blood Institute. "It will be important to understand the relationship and mechanisms, if the association is confirmed."
The team of University of Wisconsin-Madison investigators led by Nieto conducted this research in collaboration with Dr. Ramon Farré, professor of physiology at University of Barcelona, Spain. In a separate study also presented at the ATS conference, Dr. Farré's group showed that the effect of intermittent hypoxia on cancer growth is considerably stronger in lean mice than in obese mice.
The Wisconsin researchers examined 22-year mortality data on 1,522 subjects from the Wisconsin Sleep Cohort. This cohort is a longitudinal, community-based epidemiology study of sleep apnea and other sleep problems that begun in 1989 under the leadership of Dr. Terry Young, also a member of the UW population health sciences faculty. The cohort began was a random sample of Wisconsin state employees.
The participants undergo overnight sleep studies that include polysomnography - an all-night recording of sleep and breathing - and many other tests at four-year intervals. The studies are conducted in a specially designed unit at the federally funded UW Institute for Clinical and Translational Research Center (ICTR).
After adjustment for age, sex, body mass index and smoking, Nieto's study found that both all-cause and cancer mortality were associated with the presence and severity of SDB in a dose-response fashion. People with severe sleep-disordered breathing died of cancer at a rate 4.8 times higher than people with no sleep breathing problems.
These associations were similar after excluding the 126 subjects who had used continuous positive airway pressure and were stronger among non-obese subjects than obese subjects.
"In our large population-based sample, SDB was associated with an elevated risk of cancer mortality," concluded Dr. Nieto. "Additional studies are needed to replicate these results. If the relationship between SDB and cancer mortality is validated in further studies, the diagnosis and treatment of SDB in patients with cancer might be indicated to prolong survival."
Members of the Wisconsin team include Dr. Paul Peppard, the principal investigator of the Wisconsin Sleep Cohort, Dr. Terry Young, Laurel Finn and Dr. K. Mae Hla.
Date Published: 05/21/2012