At the start of the study, about 5 percent of the patients had cancer. Over an average of nearly eight years of follow-up, an additional 6.5 percent of the participants developed cancer. Most common were prostate, breast, colorectal and lung cancers, the researchers said.
Although no link was seen for cancer in general, the researchers did find that low oxygen levels related to sleep apnea were associated with smoking-related cancers, such as lung cancer.
Dr. Yosef Krespi, director of the Center for Sleep Disorders at Lenox Hill Hospital in New York City, cautioned that while sleep apnea may not cause cancer, it is a serious condition that needs to be treated.
"One should not ignore sleep apnea," Krespi said. "Sleep apnea is a chronic progressive disorder that if left untreated can result in serious heart problems."
More than 18 million American adults have sleep apnea, according to the National Sleep Foundation. Some experts say the condition is increasing because of the obesity epidemic.
Sleep apnea can make a cancer patient's life more difficult, Krespi said.
"The quality of life of sleep apnea patients with cancer and their ability to tolerate treatments such as chemotherapy and radiation can be very different than those without the condition," he said.
For more on sleep apnea, visit the U.S. National Heart, Lung, and Blood Institute.
SOURCES: Tetyana Kendzerska, M.D., Ph.D., Institute for Clinical Evaluative Sciences, Women's College Hospital, University of Toronto, Canada; Leonard Lichtenfeld, M.D., deputy chief medical officer, American Cancer Society; Yosef Krespi, M.D., director, Center for Sleep Disorders, Lenox Hill Hospital, Ne
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