People with obstructive sleep apnoea have an increased risk of Parkinson's disease, but if started early enough, continuous positive airway pressure (CPAP) may reduce that risk, according to a preliminary study presented at the American Academy of Neurology's 77th Annual Meeting taking place April 5–9, 2025, in San Diego and online.

The study found using CPAP within two years of a sleep apnoea diagnosis reduced the risk of Parkinson's.

Obstructive sleep apnoea is when throat muscles relax during sleep, blocking the airway, causing a person to wake up repeatedly to breathe. This disrupted sleep pattern can lower oxygen levels, affecting the brain. With CPAP, pressurised air is delivered through a mask to keep the airway open while a person sleeps.

"Obstructive sleep apnoea is common and previous research has found that when untreated, it is associated with an increased risk of heart attack and stroke," said study author Gregory D. Scott, MD, Ph.D., of the VA Portland Health Care System in Oregon.

"While our study found an increased risk of Parkinson's disease, the good news is people can do something about it by using CPAP as soon as they are diagnosed with the sleep disorder."

For the study, researchers reviewed more than 20 years of medical records to identify nearly 1.6 million veterans who had obstructive sleep apnoea and nearly 10 million veterans who did not.

Researchers then identified which participants developed Parkinson's disease. Of those with sleep apnoea, 5,284 people, or 3.4%, developed Parkinson's disease within five years, compared to 37,873 people, or 3.8% of those who did not have sleep apnoea.

However, Scott noted these initial proportions were potentially biased by differences in age, smoking, and overall survival between the group with sleep apnoea and those who did not have sleep apnoea.

Researchers looked at rates of Parkinson's disease five years after a sleep apnoea diagnosis. After adjusting for age, sex and health factors such as smoking, researchers found among people with sleep apnoea, there were 1.8 more cases of Parkinson's disease per 1,000 people compared to people without sleep apnoea.

Of participants with sleep apnoea, 10% had documented use of a CPAP machine. These participants were divided into two groups: those who received a CPAP machine within two years of their diagnosis and those who received one after two years.

Researchers found similar rates among people with sleep apnoea who started CPAP after two years to those who did not use CPAP, with 9.5 and 9.0 cases of Parkinson's disease per 1,000 people respectively. However, researchers found a lower rate of Parkinson's among those who started CPAP early, within two years of diagnosis, with 2.3 fewer cases per 1,000 people when compared to people who did not use CPAP.

"It is encouraging to know that while obstructive sleep apnoea may increase the risk of Parkinson's disease, treating it right away with CPAP may reduce that risk," said Scott. "Future studies are needed to follow people more closely after receiving a sleep apnoea diagnosis and over longer periods of time."

A limitation of the study was that while researchers could identify which people had a CPAP device, they were unable to tell if people used the treatment daily, as prescribed.