Oct. 7, 2024 – Think you might have sleep apnea? Here’s another reason to get tested to find out.
Emerging evidence is showing that obstructive sleep apnea (OSA) may increase the risk of some cancers, including those affecting the digestive system, kidneys, and breasts. The condition, which disrupts breathing during sleep, may carry more serious health risks than previously thought.
The latest studyon the topic, published in the Journal of Clinical Sleep Medicine, found that of 1,990 patients with sleep apnea, 181 developed cancer during the 13-year follow-up period. That’s about 9% of the patient sample, a significantly high rate, said sleep medicine specialist Ram Kishun Verma, MD, one of the study’s reviewers and co-author of a related commentary.
Previous research has found that the overall rates of cancer are about 26% higher in those diagnosed with sleep apnea compared with the general population. The more severe the sleep apnea, the higher the cancer risk, the new study found.
People with sleep apnea are “making the effort to breathe, but there's either a cessation or a reduction in airflow,” said pulmonologist Andrew Namen, MD, a professor at Wake Forest University School of Medicine. (Namen was not involved in the study.) “The different oxygen molecules essentially change your DNA, and it becomes more cancer-promoting.”
Nearly 1 billion people worldwide — and 39% of U.S. adults — are estimated to have sleep apnea. The condition is vastly underdiagnosed and undertreated — as many as 9 in 10 people with OSA don’t know they have it.
Also linked to heart disease, blood vessel issues, and neurological problems, OSA happens when the airway — the upper respiratory tract — becomes completely or partially obstructed repeatedly during sleep. During these periods, not enough oxygen gets into the body. This leads to what’s known as “intermittent hypoxemia,” alternating periods of low oxygen levels in the blood.
The lack of oxygen could trigger a cascade of biochemical reactions in the body that lead to cancer, researchers say.
How Might Sleep Apnea Lead to Cancer?
Low oxygen levels during sleep can create molecules that damage DNA, leading to harmful genetic changes and increasing the risk of cancer, said Namen.
That’s because repeated cycles of low oxygen can cause oxidative stress — an imbalance of free radicals and antioxidants. Free radicals are unstable molecules that can damage cell membranes, proteins, and DNA, triggering inflammation. To protect itself against inflammation, the body makes proteins called cytokines.
These proteins contain molecules called "cellular adhesion molecules," said Verma, a sleep doctor at Parkview Health in Fort Wayne, Indiana, and an adjunct clinical assistant professor at the Indiana University School of Medicine.
One of them — vascular cell adhesion molecule-1 (VCAM-1) — plays a significant role in the development of cancer, helping tumor cells bind to the endothelial cells that line your blood vessels and potentially cross the vessel wall. This is linked to tumor growth and the spread of cancer.
In the new study, patients underwent polysomnography, the standard test to see how severe a person’s sleep apnea is using a tool called the apnea-hypopnea index.
By taking the combined average number of times per hour the airway is completely blocked through the nose and mouth — “apnea” — and counting the number of times the airway is only partially obstructed — “hypopnea” — sleep experts can rank the severity of the condition.
The ranking is measured in events per hour. Someone with mild sleep apnea may have five to 15 events per hour during sleep, while someone with severe sleep apnea will have more than 30.
The people in the study then had their blood collected to measure levels of inflammatory biomarkers. In a subset of 427 patients, VCAM-1 was found to be elevated, along with another key biomarker: endostatin.
Endostatin stops the formation of new blood vessels, a process called angiogenesis. Tumors rely on new blood vessels to grow, so blocking this process helps slow their growth. (In fact, endostatin is being studied as a potential treatment for cancer.)
But higher endostatin levels has been linked to greater risk of cancer. Endostatin is a marker of systemic inflammation, especially in colorectal cancer.
“Both biomarkers were elevated in the samples [of patients] who later developed cancer,” said Verma.
As the severity of sleep apnea increased, so did cancer risk.
“They found that if the apnea-hypopnea index increases by 10, it’s equal to an 8% greater risk of cancer,” Verma said. Go from 20 to 40, and it’s a 16% increased risk of cancer.
Can Treating Sleep Apnea Help Prevent Cancer?
Controlling sleep apnea with proper treatment has been shown to lower other associated health risks, such as heart attack, stroke, and diabetes.
The same could be true for cancer risk, though more research is needed to know for sure, said Namen. The recent study did not look at whether treatments altered cancer risk.
Early detection is key, Namen said. Warning signs of sleep apnea include loud snoring and gasping or choking at night (often the person’s partner notices). Other red flags: morning headaches and feeling fatigued or sleepy during the day. You may be more at risk if you are overweight or have obesity, smoke or drink alcohol, or have high blood pressure or diabetes.
“Once you know you’re at risk, reach out to your primary care doctor or get directly connected to a certified sleep specialist,” Namen said.
The most common treatment is positive airway pressure (PAP) therapy — either with a CPAP machine or a BiPAP machine. Both devices help you breathe by pushing pressurized air into the lungs, opening them, and supplying the oxygen you need.
With treatment, “we see a person’s overall health care utilization goes down,” Namen said. “Their risk of motor vehicle accident crashes is reduced by almost half, and the risk of stroke and heart attack decreases.”
What’s Next
Many sleep doctors don’t regularly check for things like endostatin and VCAM-1, but preventive medicine companies can use studies like this to create prediction tools, Verma said. AI could help advance the development of such tools.
“These companies can develop prediction models to tell someone, ‘You’re at an increased risk of cancer,” said Verma. Such tools could prompt people to act quickly instead of waiting years for cancer to develop.
In the meantime, Verma would like to see more research building on the findings of the new study.
“Going forward, there is so much potential to replicate this study,” said Verma, who would like to see a larger study comparing people who control their sleep apnea with those who don’t. He’d also like researchers to track health markers like VCAM-1 and endostatin over time, noting how they change with or without treatment and how that affects cancer risk.
