When I first wrote my book, Sleep, Interrupted in 2008, I had a question mark in my diagram linking obstructive sleep apnea to possible cancer. Since that time, there have been a number of studies making that link stronger, and I am now more comfortable in removing that question mark. One of the basic hallmarks of obstructive sleep apnea is repeated episodes of low oxygen levels (intermittent hypoxia) due to obstructed breathing at night. If you google “intermittent hypoxia and cancer” you’ll see about 460,000 search results, of which 33,000 are scholarly articles. Low oxygen levels are strongly associated with cancer progression.
In a recent review article on this subject, Dr. David Gozal and colleagues published a paper titled, Sleep apnea awakens cancer: A unifying immunological hypothesis. They hypothesized that intermittent hypoxia and sleep fragmentation can promote changes in the tumor microenvironment, leading to a weakened immune system and tumor growth enhancement.
It’s important to remember that intermittent hypoxia not only can enhance cancer development, it can also in theory enhance benign tumor growth as well. One of many possible explanation is the concept of increased levels of vascular endothelial growth factor, which enhances more blood vessel growth, so that more nutrients (via blood) can reach the oxygen starved tissues. Initially, it may only cause localized enlargement of the soft tissues. Imagine if you continue to have intermittent hypoxia, and let’s say that you have a gene that makes you more susceptible to cancer. If you add additional lifestyle habits such as smoking and drinking alcohol, then one mutation can potentially lead cancer.
To date there hasn’t been any particular cancer that’s strongly associated with obstructive sleep apnea. However, one large-scale population study found that your chances of dying from cancer increases almost 5 times if you have untreated severe obstructive sleep apnea. Another study found a 2.5 times increased risk of having cancer and 3.4 times higher risk of dying from cancer with untreated moderate to severe obstructive sleep apnea.
Notice that the most common types of cancer happen in the “low priority” organs when you’re under stress. These areas include the gastrointestinal system, the reproductive organs, hands, feet, and the skin. In general, the core, central areas take priority. Any form of physiologic or emotional stress diverts blood flow and nervous system activation away from low priority to high priority areas. Rarely do you hear about cancer in the brain, heart or muscles, which are considered high priority.
This is another example of how sleep connects the dots between almost every known chronic health condition. Unfortunately, cutting edge cancer research focuses mainly on the molecular, genetic, and biochemical aspects without looking at the big picture. Without addressing proper sleep and breathing, even the best cancer treatments can give possibly suboptimal results.
If you have a diagnosis of obstructive sleep apnea, do you have a cancer history in your family?