Obstructive sleep apnea is linked to increased risk of cancer in humans: Research

According to a big study presented at the European Respiratory Society (ERS) International Congress in Barcelona, Spain, people with obstructive sleep apnea (OSA) had an increased risk of cancer.

A second research found that OSA was associated with a reduction in processing abilities in the elderly, with individuals aged 74 years or older and men showing a sharper drop in some cognitive assessments. A third research discovered that individuals with more severe OSA were more likely to develop blood clots in their veins, which might be fatal.

OSA is a common sleep condition in which persons have partial or total blockage of their airways while sleeping and stop breathing multiple times during the night. This can be characterised by loud snoring, gasping, choking, and daytime tiredness. It is estimated that 7-13% of the population is affected. People who are overweight or obese, have diabetes, or smoke or drink excessively are more likely to develop OSA.

The first study’s presenter, Dr Andreas Palm, a researcher and senior consultant at Uppsala University in Sweden, said: “Patients with obstructive sleep apnea have an increased risk of cancer, but it is unclear whether this is due to the OSA itself or to other cancer risk factors such as obesity, cardiometabolic disease, and lifestyle factors. Our data suggest that oxygen deprivation caused by OSA is related with cancer on its own.”

Dr. Palm and colleagues examined data from 62,811 individuals in Sweden five years before they began therapy for OSA. Patients were treated with continuous positive airway pressure (CPAP) between July 2010 and March 2018, which delivers a positive pressure of air through a mask to keep the airways open during sleep. The researchers combined this data with information from the Swedish National Cancer Registry and statistics from Statistics Sweden.

The researchers considered factors that may influence the outcomes, such as body size, other health issues, and socioeconomic level. They compared 2,093 individuals with OSA and a cancer diagnosis up to five years before OSA diagnosis with 2,093 patients with OSA but no cancer.

The apnoea hypopnea index (AHI), which evaluates the amount of breathing interruptions during sleep, or the oxygen desaturation index (ODI), which measures how many times each hour levels of oxygen in the blood fall by at least 3% for ten seconds or longer, were used to assess the severity of OSA.

“We discovered that cancer patients had somewhat more severe OSA, as indicated by an apnea hypopnea index average of 32 against 30, and an oxygen desaturation index average of 28 versus 26,” he stated. “Further subgroup analysis revealed that ODI was greater in patients with lung cancer (38 against 27), prostate cancer (28 versus 24), and malignant melanoma (38 versus 24). (32 versus 25).

“The findings of this study emphasise the need of treating untreated sleep apnea as a risk factor for cancer and for clinicians to be aware of the possibility of cancer while treating OSA patients. However, our findings do not support or encourage expanding cancer screening to all OSA patients.”

The study only looked at data from a single moment in time, thus it cannot prove that OSA causes cancer, simply that it is linked to it. The study did not capture certain significant lifestyle characteristics like as physical activity and eating choices on an individual basis. The study’s key strength is its vast size and good quality data on cancer diagnosis and OSA.

Dr. Palm and his colleagues intend to expand the number of patients and follow them over time to investigate the possible effects of CPAP treatment on cancer incidence and survival. “The relationship between OSA and cancer is less well established than the link between OSA and heart and blood vessel disease, insulin resistance, diabetes, and fatty liver disease,” he explained. “As a result, additional research is required, and we hope that our work will stimulate other academics to investigate this vital subject.”

Professor Raphael Heinzer, director of the Centre for Investigation and Research on Sleep (CIRS) at Lausanne University in Switzerland, told the congress in a second presentation [2] that a study conducted by his colleague Dr Nicola Marchi found that OSA was associated with a greater decline in mental processing powers over a five-year period.

Professor Heinzer, Dr. Nicola Marchi of Lausanne University Hospital, and colleagues evaluated persons aged 65 and above from the Lausanne general population who were recruited to the CoLaus/PsyCoLaus and HypnoLaus investigations between 2003 and 2008 and followed up every five years. When they entered the research, 358 people were given a sleep test to see if they had OSA and how severe it was.

Their mental processing abilities were also examined during the first follow-up, which took place between 2009 and 2013, and another cognitive evaluation took place five years later.

The cognitive tests measured global cognitive function (knowledge and reasoning abilities), processing speed (the time it takes to understand and react to information), executive function (the ability to organise thoughts and activities, prioritise tasks, and make decisions), verbal memory, language, and visual perception of spatial relationships between objects (visuospatial function).

“We discovered that OSA, and particularly reduced oxygen levels during sleep owing to OSA, was related with a higher loss in general cognitive function, processing speed, executive function, and verbal memory,” Dr Marchi stated before the congress.

In several specific cognitive tests, we also discovered that adults aged 74 and older, as well as men, were at a greater risk of cognitive impairment due to sleep apnea.”

The Stroop test, which assesses processing speed and executive function, for example, revealed a greater drop in those aged 74 and older compared to younger participants, whereas the verbal fluency test revealed a steeper decline in males but not in women.

“This study shows that sleep apnea severity and night-time oxygen deprivation contribute to cognitive impairment in old age.” It also demonstrates that sleep apnea is associated with a decline in specific cognitive functions, such as processing speed, executive function, and verbal memory, but not with a decline in all cognitive functions; for example, language and visuospatial function were not affected,” Dr Marchi explained.

“People with OSA, as well as clinicians, should be informed that OSA may contribute to cognitive loss.” However, no strong evidence has been found that treating OSA with continuous positive airway pressure (CPAP) prevents cognitive deterioration.

“Our findings imply that not all OSA patients are at the same risk of cognitive decline; there is likely a subset of patients, notably those with greater nocturnal oxygen deprivation, but also older patients and men, who are at higher risk of OSA-related cognitive decline,” he added.

The researchers want to analyse data on the impact of OSA after 10 years to learn more about who is more vulnerable to cognitive deterioration caused by OSA. Dr. Marchi believes that the next step should be to conduct a randomised controlled study with these individuals to explore the effect of CPAP on cognition.

The study’s strengths include the fact that it tracked patients for five years, that OSA was assessed using the “gold standard” polysomnography test, and that numerous tests were utilised to examine a variety of cognitive activities. The patients were reasonably healthy, with no serious cognitive impairment or dementia, and OSA was only tested at the start of the trial.

Professor Wojciech Trzepizur of Angers University Hospital in France presented a third research, which found that individuals with more severe OSA, as defined by AHI and signs of nocturnal oxygen deprivation, were more likely to develop venous thromboembolism (VTE). VTEs were diagnosed in 104 of the 7,355 individuals who were followed for more than six years.

“This is the first study to look at the link between obstructive sleep apnea and the occurrence of spontaneous venous thromboembolisms. We discovered that individuals who spent more than 6% of their nighttime with blood oxygen levels below 90% of normal had a nearly two-fold chance of getting VTEs as compared to patients who did not have oxygen deprivation “Professor Trzepizur said “Further research is needed to determine if effective therapy for OSA, such as CPAP, may minimise the incidence of VTEs in individuals with severe nocturnal oxygen deprivation.”

Professor Winfried Randerath of the University of Cologne’s Bethanien Hospital is the leader of the ERS specialised group on sleep disordered breathing and was not engaged in the three investigations.

He stated, ” “These three investigations reveal concerning links between obstructive sleep apnea and serious disorders that influence survival and quality of life. The findings back up the importance of sleep apnea in cancer, venous thromboembolisms, and mental health.

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While scientists cannot establish that OSA causes any of these health issues, people should be made aware of these connections and should strive to adopt lifestyle adjustments to lower their risk of OSA, such as keeping a healthy weight. If OSA is suspected, a proper diagnosis and therapy should be begun. We look forward to more research that will assist to establish if OSA is driving some of the health issues observed in these trials.”

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