A new discovery about the way sleep apnea may raise
the risk of heart disease also suggests that taking cholesterol-lowering statin
drugs might reduce that risk, according to a new study.
Sleep apnea is a common disorder that involves
irregular breathing while asleep, with oxygen intake dropping frequently for
brief periods. The condition can triple a person's risk of stroke, high blood
pressure and other heart problems, said study author Dr. Sanja Jelic, an
associate professor of medicine at Columbia University Medical Center in New
York City.
Statins such as Crestor (rosuvastatin) and Lipitor
(atorvastatin) are already taken by millions of Americans to reduce their risk
of heart disease.
"If the beneficial effects of statins on blood
vessel health in patients with obstructive sleep apnea is confirmed in larger
clinical trials, obstructive sleep apnea may become an indication for statin
therapy," Jelic said.
The findings were published online Jan. 6 in the
journal Science Translational Medicine.
In the small, laboratory study, researchers closely
examined endothelial cells, which line the inside of blood vessels. They looked
at endothelial cells from 76 adults with obstructive sleep apnea and 52 adults
without sleep apnea. The adults were similar in terms of body fat percentage,
daytime sleepiness symptoms, blood pressure and underlying health conditions.
The scientists found that a particular protein was
in different places in the cells of those with sleep apnea compared to the
cells of those without the disorder. The protein, called CD59, normally stays
on the surface of endothelial cells to protect them from part of the body's
immune system, according to background notes with the study. But in patients
with sleep apnea, the protein was often inside the cells.
A series of experiments showed that the cells pull
the protein inside them when oxygen levels drop. The cells then become
vulnerable to inflammation, which can contribute to high blood pressure, the
researchers said.
"Chronic inflammation of the blood vessels
contributes to increased cardiovascular risk, such as heart attack, stroke or
heart failure, in patients with obstructive sleep apnea," Jelic said.
How much
protein the cells pulled inside them depended on how much cholesterol --- the
waxy, fat-like substance found in all cells of the body -- was present. Statins
stopped the cells from bringing the protein inside them, the investigators
found.
The findings could help to connect the dots for
health care experts, said Rebecca Spencer, an associate professor of
psychological and brain sciences at the University of Massachusetts, who wasn't
involved in the study.
"This presents an explanation of how apnea and
vascular risk are connected," Spencer said. "There is some assumption
that these two may be independently associated with poor health, but this study
shows a mechanism that directly links apnea to vascular risk."
Experts agreed, however, that people with sleep
apnea should not seek statin prescriptions just yet since these findings were
limited to the lab.
Dr. Sarah Samaan, a cardiologist at the Baylor Heart
Hospital in Plano, Texas, said: "This is basic science research, not a
clinical study. So we don't know specifically what degree of reduction in heart
risk statins might provide for sleep apnea patients without other risk factors.
But it does provide a great launching point for new patient-centered studies on
the topic.
"Although statins don't treat sleep
apnea, they may help reduce the dangerous consequences sleep apnea can have on
the heart," she added.
Possible side effects of statins can include muscle
aches or liver enzyme abnormalities in about 5 percent of patients, said
Samaan, who played no role in the study. More serious side effects, such as
muscle breakdown related to kidney failure, are rare, she said.
The primary treatment for obstructive sleep apnea is
continuous positive airway pressure (CPAP), delivered through a mask worn at
night, Spencer said. Weight loss and a healthy lifestyle can also help treat
sleep apnea.
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