Two new studies have found that people with sleep apnea, a
common disorder that causes snoring, fatigue and dangerous
pauses in breathing at night, have a higher risk of cancer.
The new research marks the first time that sleep apnea has
been linked to cancer in humans. About 28 million Americans have
some form of sleep apnea, though many cases go undiagnosed.
For sleep doctors, the condition is a top concern because it
deprives the body of oxygen at night and often coincides with
cardiovascular disease, obesity and diabetes.
“This is really big news,” said Joseph Golish, a professor
of sleep medicine with the MetroHealth System in Cleveland who
was not involved in the research.
Golish, the former chief of sleep medicine at the Cleveland
Clinic, said that the cancer link may not prove to be as strong
as the well-documented relationship between sleep apnea and
cardiovascular disease, “but until disproven, it would be one
more reason to get your apnea treated or to get it diagnosed if
you think you might have it”.
In one of the new studies, researchers in Spain followed
thousands of patients at sleep clinics and found that those with
the most severe forms of sleep apnea had a 65% greater risk of
developing cancer of any kind. The second study, of about 1,500
government workers in Wisconsin, showed that those with the most
breathing abnormalities at night had five times the rate of
dying from cancer as people without the sleep disorder. Both
teams only looked at cancer diagnoses and outcomes in general,
without focusing on any specific type of cancer.
In both studies researchers ruled out the possibility that
the usual risk factors for cancer, like age, smoking, alcohol
use, physical activity and weight, could have played a role. The
association between cancer and disordered breathing at night
remained even after they adjusted these and other variables.
Mitesh Borad, a cancer researcher and assistant professor of
medicine at the Mayo Clinic who was not involved with the
studies, called the findings “provocative” but said more
research was needed to confirm the association.
Recent animal studies have suggested that sleep apnea might
play a role in cancer. When mice with tumors were placed in
low-oxygen environments that simulate the effects of sleep
apnea, their cancers progressed more rapidly. Scientist
speculate that depriving mice of oxygen may cause their bodies
to develop more blood vessels to compensate, an effect that
could act as a kind of fertilizer for cancer tissue and cause
tumors to grow and spread more quickly. Researchers wondered
whether a similar relationship might exist in humans.