Snoring increases the risk of cancer, dementia and cardiovascular disease, according to scientists. The research was shared at a European Respiratory Society meeting in Barcelona.
Snoring cuts off the supply of oxygen, which can fuel the growth of tumours and blog clots. It can also increase the loss of brain cells.
The study focused on obstructive sleep apnoea (OSA), which affects around 1.5 million Britons. OSA occurs when the walls of the throat relax and narrow, interrupting a person's normal breathing during the night.
Dr Andreas Palm, of Uppsala University, said: "It's known already patients with obstructive sleep apnoea have an increased risk of cancer. But it has not been clear whether or not this is due to the OSA itself or to related risk factors for cancer, such as obesity, cardiometabolic disease and lifestyle factors. Our findings show that oxygen deprivation due to OSA is independently associated with cancer."
OSA blights the lives of up to one-in-eight people. Diabetics, smokers and drinkers are also vulnerable. Twice more common in men than women it can begin at any time - including childhood and many sufferers are unaware they have it.
Overweight individuals are particularly prone to OSA. Preventative measures include shedding the pounds or wearing a mask in bed which blows air into the back of the throat.
Dr Palm's team analysed data on 62,811 Swedes five years before they started being treated for OSA with a CPAP (continuous positive airway pressure) mask. They combined it with information from the Swedish National Cancer Registry - taking into account body size, other health problems and socio-economic status.
It enabled them to match 2,093 patients with OSA and a diagnosis of cancer up to five years before OSA diagnosis with a control group of 2,093 patients with OSA but no cancer. Severity was measured with the apnoea hypopnea index (AHI) which counts breathing disturbances during sleep or the oxygen desaturation index (ODI) - how many times an hour blood levels fall by at least three per cent for ten seconds or longer.
Dr Palm said: "We found patients with cancer had slightly more severe OSA, as measured by an apnoea hypopnea index average of 32 versus 30, and an oxygen desaturation index of 28 versus 26. In further analysis of subgroups, ODI was higher in patients with lung cancer (38 versus 27) prostate cancer (28 versus 24) and malignant melanoma (32 versus 25).
"The findings in this study highlight the need to consider untreated sleep apnoea as a risk factor for cancer and for doctors to be aware of the possibility of cancer when treating patients with OSA. However, extending screening for cancer to all OSA patients is not justified or recommended by our study results."
The researchers plan to increase the number of patients and follow the patients over time to study the potential influences of CPAP treatment on cancer incidence and survival.
Dr Palm said: "The association between OSA and cancer is less well established than the link with diseases of the heart and blood vessels, insulin resistance, diabetes and fatty liver disease. Therefore, more research is needed, and we hope our study will encourage other researchers to research this important topic."
