While the causal nature of the links is unclear, they underscore the need to reduce the risk of developing the condition.
People living with obstructive sleep apnoea face a higher risk of cancer, cognitive decline and venous thrombosis, several new studies suggest.
“Three studies show worrying associations between obstructive sleep apnoea and important diseases that affect survival and quality of life,” Professor Winfried Randerath, head of the European Respiratory Society specialist group on sleep disordered breathing, said in a statement.
“While 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 in order to reduce their risk of OSA, for instance, by maintaining a healthy weight,” he said about the research, presented at the European Respiratory Society International Congress in Spain last month.
One Swedish study analysed data from 63,000 patients initiating CPAP therapy, and crosslinked this with cancer registry and demographic data.
They found that patients who developed cancer in the five years before starting PAP treatment were more likely to have more severe obstructive sleep apnoea, indicated by higher apnoea hypopnoea and oxygen desaturation index averages, than matched OSA patients who didn’t develop cancer.
The oxygen desaturation index measures how many times each hour that blood oxygen levels fall by 3% or more for at least ten seconds.
“It is known already that 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” study author Dr Andreas Palm, senior consultant at Uppsala University, said in a statement.
“Our findings show that oxygen deprivation due to OSA is independently associated with cancer.”
A further subgroup analysis showed oxygen desaturation index was significantly higher in patients with lung cancer (38 compared to 27), prostate cancer (28 compared to 24) and malignant melanoma (32 compared to 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.”
Obstructive sleep apnoea was also tied to cognitive decline in a second study of 358 relatively healthy participants aged 65 and over who had no dementia or severe cognitive impairment.
Participants were given a sleep test, as well as several assessments of mental processing power, and then these cognitive tests were performed again around five years later.
Researchers discovered that OSA itself, and low levels of oxygen saturation caused by the condition, were linked to steeper declines in global cognitive function, processing speed, verbal memory and executive function compared to patients who were less affected by OSA.
Processing speed and executive function was even more affected in men than women, and in those over the age of 74 compared to younger participants.
“This study demonstrates that the severity of sleep apnoea and night-time oxygen deprivation contribute to cognitive decline in old age,” Dr Nicola Marchi said ahead of the conference.
“People with OSA and doctors should be aware that OSA may play a role in cognitive decline. However, to date, OSA treatment with continuous positive airway pressure (CPAP) has not been clearly demonstrated to prevent cognitive decline.
“Our study suggests that probably not all OSA patients have the same risk of cognitive decline; there is probably a subgroup of patients, particularly those with greater nocturnal oxygen deprivation but also older patients and men, who could be at greater risk of OSA-related cognitive decline,” he said.
The third study presented at the congress assessed the likelihood of venous thromboembolism (VTE) among patients with severe obstructive sleep apnoea.
Among the more than 7000 patients with severe apnoea evaluated over a six-year follow-up period, just over 100 developed venous thrombosis. The risk of developing VTEs almost doubled among those who had oxygen saturation levels in their blood below 90% for more than 6% of the time they slept.
“This is the first study to investigate the association between obstructive sleep apnoea and the incidence of unprovoked venous thromboembolisms.
“Further studies are required to see whether adequate treatment for OSA, for instance with CPAP treatment, might reduce the risk of VTEs in patients with marked nocturnal oxygen deprivation,” Professor Wojciech Trzepizur said ahead of the presentation.
Obstructive sleep apnoea is believed to affect between 7-13% of the population worldwide, with greater risks among those who are overweight, smokers and people with diabetes.
