Sleep disordered breathing (SBD) is linked to many health-related illnesses, including hypertension, cardiovascular disease, and depression. A new study, for the first time, associates conditions such as sleep apnea to an increased risk of cancer complications, including mortality.
Dr. F. Javier Nieto, chair of the Department of Population Health Studies at the University of Wisconsin School of Medicine and Public Health, and colleagues studied over 1,500 subjects enrolled in the Wisconsin Sleep Cohort, a community-based study that began in 1989. Each underwent overnight monitoring that included polysomnography, an overnight recording of sleep and breathing, every four years at the federally funded UW Institute for Clinical and Transitional Research Center (ICTR).
Over the course of the 22-year study, those with severe SBD had five times higher incidence of cancer deaths.
Moderate to severe obstructive sleep apnea is associated with an increased risk of death from any cause in middle-aged adults, note the National Heart, Lung, and Blood Institute (NHLBI), but most often, the cause of mortality is heart disease. The researchers believe that cancer risk is tied to lack of oxygen or anaerobic cell activity over long periods of time. Animal studies have tied inadequate supply of oxygen, also known as intermittent hypoxia, to the promotion of tumor growth.
During apnea episodes, the muscles in the back of the throat relax, narrowing or closing the airway, causing a momentary cessation of breathing. This may lower the level of oxygen in the blood and ultimately all body tissues.
Dr. Nieto warns, though, that “Clearly, there is a correlation (but) we are a long way from proving that sleep apnea causes cancer or contributes to its growth.” The study results were presented at the American Thoracic Society 2012 International Conference in San Francisco on May 20th.
Treatment and management of sleep apnea is recommended in all patients, but also, Dr. Nieto notes, might be part of the plan for prolonging survival in cancer patients. A separate Australian study also presented at the ATS Conference finds that sleep disordered breathing may be successfully managed within a primary care setting, eliminating the obstacle of long waiting times to visit a specialist in sleep services.
"With adequate training of PCPs and their practice nurses and appropriate funding models to support an ambulatory strategy, primary care management of OSA has the potential to reduce the burden of disease in the community by improving patient access to sleep services,” said lead author Ching Li Chai-Coetzer MBBS of the Adelaide Institute for Sleep Health at Repatriation General Hospital. “This would be particularly beneficial for rural and remote regions, as well as developing nations, where access to specialist services may be limited."
Source: ATS 2012 International Conference in San Francisco, California. May 18 – 23, 2012.