Snorers face a significantly higher risk of cancer, heart disease, dementia
UPPSALA, Sweden — According to new research, snorers may be at increased risk of cancer, cardiovascular disease and dementia. Swedish scientists claim that obstructive sleep apnea, of which snoring is the main symptom, cuts off the supply of oxygen, which fuels tumours, blood clots and loss of brain cells.
Obstructive sleep apnea (OSA) affects around 30 million Americans – although only 6 million are diagnosed cases, according to the American Medical Association. The condition causes the walls of the throat to loosen and narrow, interrupting normal breathing several times a night. Overweight people are particularly prone to OSAS. Preventative measures include losing weight or wearing a mask in bed that blows air into the back of your throat.
The results, presented at the European Respiratory Society (ERS) meeting in Barcelona, could lead to screening programs. They are based on three studies conducted across Europe.
“Patients with obstructive sleep apnea are already known to have an increased risk of cancer, but whether or not this is due to OSA itself or to cancer risk factors has not been clear. related factors, such as obesity, cardiometabolic diseases and lifestyle factors,” says Dr. Andreas Palm, senior researcher and consultant at Uppsala University, in a statement. Oxygen deprivation due to OSA is independently associated with cancer.”
The study authors analyzed data from 62,811 Swedes five years before they started being treated for obstructive sleep apnea 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 conditions and socioeconomic status. It allowed them to match 2,093 patients with OSA and a cancer diagnosis 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 Apnea Hypopnea Index (AHI) – which counts breathing disturbances during sleep – or the Oxygen Desaturation Index (ODI), which measures how many times per hour blood levels drop d at least three percent for ten seconds or more.
“We found that cancer patients had slightly more severe OSA, as measured by an average apnea-hypopnea index of 32 versus 30, and an oxygen desaturation index of 28 versus 26,” says Palm. “In further subgroup analysis, ODI was higher in patients with lung cancer (38 vs 27), prostate cancer (28 vs 24) and melanoma clever (32 versus 25).
“The results of this study underscore the need to consider untreated sleep apnea as a risk factor for cancer and for physicians to be aware of the possibility of cancer when treating patients with OSA,” continues Palm. “However, extending cancer screening to all patients with OSA is neither justified nor recommended by the results of our study.”
The researchers plan to increase the number of patients and follow patients over time to study the potential influences of CPAP treatment on cancer incidence and survival.
“The association between OSA and cancer is less well established than the link with heart and blood vessel disease, insulin resistance, diabetes, and fatty liver disease,” adds Palm. “Therefore, more research is needed, and we hope our study will encourage other researchers to research this important topic.”
The impact of obstructive sleep apnea on the brain
A second study identified a link between OSA and a greater decline in brain power over a five-year period. It was based on sleep tests carried out by 358 people over the age of 65 in Switzerland. Global cognitive and executive functions, verbal memory, language, and visual perception of spatial relationships were also assessed.
“We found that OSA and, in particular, low oxygen levels during sleep due to OSA, were associated with greater declines in overall cognitive function, processing speed, function executive and verbal memory,” explains Dr Nicola Marchi from the University of Lausanne. “We also found that people aged 74 and older and men were at higher risk of sleep apnea-related cognitive decline in some specific cognitive tests.”
For example, the Stroop test, which measures processing speed and executive function, showed a steeper decline in people aged 74 and older compared to younger participants. Verbal fluency showed a more pronounced decline in men, but not in women.
“This study demonstrates that the severity of sleep apnea and nocturnal oxygen deprivation contribute to cognitive decline in the elderly,” says Dr. Marchi. “It also shows that sleep apnea is linked to a decline in specific cognitive functions, such as processing speed, executive function and verbal memory, but not to a decline in all cognitive functions; for example, language and visuospatial function were unaffected.
“People with OSA and physicians should be aware that OSA may play a role in cognitive decline. However, to date, it has not been clearly demonstrated that OSA treatment with continuous positive airway pressure (CPAP ) prevents cognitive decline,” says Marchi. “Our study suggests that probably not all OSA patients have the same risk of cognitive decline; there is likely a subset of patients, particularly those who suffer from greater severe nocturnal oxygen deprivation, but also older patients and men, who may be at higher risk for OSA-related cognitive decline.
The researchers plan to analyze data on the impact of OSA after ten years to learn more about who is most at risk for cognitive decline. Dr. Marchi suggests performing a randomized controlled trial with these patients to study the effect of CPAP on cognition should be the next step after that.
Higher risk of blood clots
A third study showed that patients with more severe obstructive sleep apnea, as measured by AHI and markers of nocturnal oxygen deprivation, were more likely to develop blood clots (venous thromboembolism) which can trigger heart attacks or strokes.
“This is the first study to investigate the association between obstructive sleep apnea and the incidence of unprovoked venous thromboembolism,” says Wojciech Trzepizur, from the University Hospital of Angers in France. “We found that those who spent more than 6% of their night with blood oxygen levels below 90% of normal had an almost double risk of developing VTE compared to patients without oxygen deprivation. Further studies are needed to see if adequate treatment of OSA, for example with CPAP therapy, could reduce the risk of VTE in patients with marked nocturnal oxygen deprivation.
The results were based on 7,355 patients followed for more than six years, 104 of whom developed VTE.
Professor Winfried Randerath, from the Bethanien Hospital of the University of Cologne, Germany, is the head of the ERS specialist group on sleep-disordered breathing and was not involved in the three studies. “These three studies show disturbing associations between obstructive sleep apnea and important diseases that affect survival and quality of life,” he says. “The data supports the relevance of sleep apnea to cancer, venous thromboembolism and mental health. Although they cannot prove that OSA causes any of these health problems, people should be made aware of these links and should try to make lifestyle changes to reduce their risk of OSA, for example maintaining a healthy weight.
“However, if OSA is suspected, a definitive diagnosis and treatment should be initiated,” he stresses. “We look forward to further research that may help clarify whether OSA may be the cause of some of the health issues observed in these studies.”
South West News Service writer Mark Waghorn contributed to this report.