Sleep apnoea and cancer
Sleep apnoea is a common breathing disorder in which the upper airway collapses repetitively throughout the night leading to low oxygen levels and disrupted sleep. The most common treatment is continuous positive airway pressure (CPAP) therapy.
CPAP is highly effective in reducing overnight breathing disturbances in patients with sleep apnoea. However, many patients are unable to tolerate CPAP therapy, so new treatment options are required because untreated sleep apnoea has been linked to increased risk of neurocognitive impairment, motor vehicle accidents, and a range of cardiovascular diseases including hypertension and stroke.
And recent studies have also shown that people with sleep apnoea may have a higher risk of cancer incidence and cancer-related death.
A community-based cohort study from the University of Wisconsin suggests a strong association between those suffering with sleep apnoea and cancer mortality. The study looked at 1522 subjects and reviewed mortality over a follow up period of 22 years. Data were adjusted to take age, sex, body mass index and smoking into account. Researchers found that sleep apnoea severity increased the likelihood of dying from cancer.
Those suffering from moderate apnoea (where the upper airway closes or severely narrows between 15-29.9 times per hour of sleep) had double the risk of cancer death whereas those with severe sleep apnoea (≥ 30 events per hour of sleep) had 4.8 times higher risk of dying from cancer when compared to people without the sleep disorder.
In another cohort study from Spain, researchers showed that people with sleep apnoea were more likely to develop cancer than people who had fewer oxygen drops during the night. However, the association between sleep apnoea and increased cancer incidence disappeared when results were adjusted for age, gender and body mass index.
Both studies were sparked by findings that intermittent periods of low oxygen (hypoxia) enhances tumor progression in a mouse model of obstructive sleep, most likely mediated by enhanced vascular growth.
Future studies are needed to validate the association between cancer, sleep apneoa, and the impact of sleep apnoea treatment in cancer patient survival. We are conducting several studies in people with and without sleep apnoea at NeuRA to investigate the causes and consequences of sleep apnoea as well as studies aimed at developing new treatment options for patients.
Dr Danny Eckert is a neurophysiologist and expert in sleep apnoea.
Dr Jayne Carberry is a research assistant with the Eckert group at NeuRA.