A study led by Dr. F. Javier Nieto and his team of researchers at the University of Wisconsin-Madison School of Medicine and Public Health suggest that people with severe sleep-disordered breathing (SDB) or sleep apnea are nearly five times more likely to die of cancer than people without sleep apnea.
Sleep apnea is characterized by interrupting breathing during sleep. People with untreated sleep apnea stop breathing repeatedly during their sleep. This in turn may cause hypoxia to the brain and the rest of the body. While previous studies have revealed that sleep apnea can contribute to cardiovascular disease, depression, and early death, it may now be a link to cancer.
The Wisconsin team examined 22-year mortality data on approximately 1,500 subjects from a sleep study that began in 1989. This cohort was a random sample of Wisconsin state employees. After adjustment for age, sex, body mass index, and smoking, Nieto’s team discovered that these contributing factors, along with cancer mortality, were associated with the presence of severe SDB. When excluding the non-obese patients that were treated with CPAP (Continuous Positive Airway Pressure), the cancer risk was stronger than compared with the obese subjects.
Researchers have stated that they are a long way from proving that sleep apnea causes cancer. With that being said, animal studies suggest that sleep apnea may promote angiogenesis or increased vascular growth, therefore leading to tumor growth -- cancer cells may generate blood vessel growth in order to survive in a hypoxic environment. They also suggest that SDB is associated with an increased risk of cancer mortality in humans.
There is obviously more research that needs to take place before we can officially make the claim that severe SDB causes cancer, but in the meantime, could we help identify patients with severe SDB and encourage them to seek out proper treatment?
Most clinicians will be able to identify patients with existing common risk factors for sleep apnea:
- History of smoking or current smoker
- Older adult
- Excessive alcohol use
As we shift our thinking towards preventive medicine, this is just one more area we can focus a little more attention on in an effort to help reduce the incidence of cancer.
For full review of this article, please visit Sleep Apnea Associated with Higher Mortality from Cancer or Campus Connection: UW study links sleep apnea to higher mortality from cancer.