- People with obstructive sleep apnea have an increased risk of developing long COVID.
- Obstructive sleep apnea is a fairly common condition that affects about 29.4 million adults in the U.S., and is characterized by gasping or snoring during sleep.
- Many risk factors for sleep apnea—including being older and having obesity—are also risk factors for COVID-19 outcomes.
Having obstructive sleep apnea could increase a person’s chance of getting long COVID by as much as 75%, new research shows, suggesting that people with sleep apnea who receive a COVID-19 diagnosis may benefit from additional monitoring.
The research, published in Sleep on May 11, looked at databases of 1.8 million and 330,000 adults. A third data set tracked 106,000 kids. All participants tested positive for COVID between March 2020 and February 2022.
Though the link did not seem to exist for children, the researchers found that adults with obstructive sleep apnea (OSA) were much more likely to experience long COVID symptoms as compared to those without OSA. In the larger data set, people with OSA had up to a 75% increased risk of getting long COVID after an infection, while in the smaller data set of adults saw a 12% increased risk.
“What we really took away from this analysis importantly, is that both studies—even after accounting for many other factors—showed an elevated risk,” Lorna Thorpe, PhD, MPH, the study’s senior author and professor and director of the division of epidemiology at the NYU Grossman School of Medicine, told Health.
The study also found that, in the larger data set, women with OSA were more likely to get long COVID than men with the condition. The study is part of the National Institutes of Health RECOVER (Researching COVID to Enhance Recovery) Initiative, a $1.15 billion program investigating COVID and long COVID.
Here’s what experts had to say about the results of the study, how long COVID and obstructive sleep apnea might be linked, and what people can do to stay safe.
Sleep Apnea Show to Increase Risk of Long COVID
Obstructive sleep apnea is a fairly common condition that affects about 29.4 million adults in the U.S. It’s characterized by gasping or snoring, which is caused by a blocked upper airway. A person’s breathing usually stops and starts frequently throughout the night, and results in poor sleep and low levels of oxygen in the body.
The parameters for long COVID are not so neatly defined, however. The condition can last for several weeks to years, and people can experience a wide range of symptoms, everything from fatigue to respiratory issues to brain fog.
This made Thorpe’s and her team’s study a bit more complicated, she explained.
“We have no formal case definition for long COVID. And as people know, long COVID can have many different manifestations. So some studies tend to apply a more stringent criteria,” she said. “Others draw a broader definition to make sure they’re not missing anyone.”
This variety in definitions is reflected in the results of the study, she added. Thorpe and her colleagues looked at over 2.2 million patients who had tested positive for COVID in one of three different data sets. The patients had all tested positive for COVID between March 2020 and February 2022.
Researchers also identified those who had already been diagnosed with OSA—about 5% of adults and less than 2% of children—and used machine learning to determine who likely had long COVID through assessing follow-up symptoms and medial visits.
Though the findings were different for both adult data sets, they indicated a similar consensus: Adults with OSA who were diagnosed with COVID were more likely to go on to develop long COVID. In the largest data set, which included 1.78 million patients, people with sleep apnea were 75% more likely to develop long COVID. In the smaller adult data set of just over 333,000 patients, sleep apnea increased the risk of long COVID by 12%.
These increased risks were not seen among children. After controlling for other medical conditions, including obesity, there were no significant links between sleep apnea and long COVID in children.
Among adults with sleep apnea, the discrepancy between data sets in people who went on to develop long COVID could be due to the definitions of long COVID that were used. “We had a stringent definition and a broad definition,” Thorpe said. “The more stringent definition found the higher risk, and a broader definition found a slightly lower risk.”
In other words, the smaller study identified more adults as having long COVID, so a smaller percentage were sleep apnea patients, therefore the risk of long COVID was lower. With a more stringent definition of long COVID, fewer adults were identified as having long COVID, but a higher percentage were sleep apnea patients, showing an increased risk of long COVID.
The true risk of long COVID in people with sleep apnea is still unknown. “We can’t say for certain which [data set] is more correct,” Thorpe said. “If there’s a truth out there, it’s probably in between these two studies.”
Beyond the general increased risk for OSA patients, the study also found that the chance of getting long COVID was higher for women with sleep apnea. In the 1.78 million-person data set, women had an 89% higher chance of getting long COVID if they had OSA, as compared to a 59% higher chance for men.
“Most studies of long COVID have a female predominance,” Kingman P. Strohl, MD, professor of physiology, biophysics, and oncology at the Case Western Reserve University School of Medicine, and senior attending physician at University Hospitals Cleveland Medical Center, told Health in a statement.
Women having a higher incidence of long COVID could be due to biological reasons, Dr. Strohl posited, or women may be more likely to seek medical attention or admit that they’re having issues with fatigue.
The other possible explanation is that “sleep apnea has historically been considered a male disease, and so women are often under-diagnosed,” Thorpe said. The women who do have an OSA diagnosis, then, probably have much more severe cases, she added, which could lead to worse long COVID.
What Causes Sleep Apnea?
How Are Long COVID and Sleep Apnea Connected?
The goal of the study was simply to establish whether there was a link between sleep apnea and long COVID, but there are a few ways in which the sleep disorder could have an effect on a person’s experience with COVID.
For one, Thorpe and Dr. Strohl agreed, the connection between OSA and long COVID could be explained by some sort of underlying factor putting someone at risk for both conditions. In fact, many risk factors for sleep apnea are also risk factors for COVID-19 outcomes, Thorpe said in a press release.
“People with sleep apnea tend to have higher rates of obesity and hypertension and other cardiovascular problems. And these are also common risk factors for severe acute COVID, and have been implicated as risk factors for long COVID,” said Thorpe.
Another possibility, however, is that sleep apnea affects people’s bodies in such a way that they’re more likely to be a long hauler.
Sleep apnea reduces the amount of oxygen in the blood, which is called hypoxemia, Thorpe explained. This can also be an issue with COVID infections, she said, so people with sleep apnea might have worse COVID symptoms. These severe infections more frequently lead to long COVID.
OSA has also been shown to worsen the body’s immune system.
“Sleep apnea can also result in increased inflammation and a greater propensity to develop infection,” Thorpe said. “So it really does seem like there is a constellation of risk factors that are common for sleep apnea and long COVID, and also a constellation of symptoms that are common.”
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One Step Toward Better Understanding Long COVID
At this point, there are a number of unanswered questions about long COVID. But the study does prompt more jumping off points for more research, Thorpe said.
The study wasn’t able to look into which specific type of long COVID symptoms OSA is most closely associated with, she said, whether that be respiratory and heart issues, digestive issues, neurological issues, or a range of other symptoms. But there are a host of other related questions.
“Does the severity of your sleep apnea influence your risk? Does the variant of SARS COV2 influence that risk?” she asked. “How protective is the vaccine? So these are some of the questions that prospective studies can look into.”
But until those questions are answered, the study at the very least emphasizes the importance of getting vaccinated and avoiding COVID infection, especially for people with OSA, Thorpe said.
Plus, OSA is frequently underdiagnosed—it’s estimated that nearly a billion adults worldwide could have the condition. So people should be on the lookout for snoring, unrefreshing sleep, excessive tiredness during the day, and other possible symptoms of OSA, Dr. Strohl said, and seek help from a medical provider.
“People with sleep apnea are recommended to keep current with their recommended vaccinations. And if they are infected with [the] COVID-19 virus, they should obtain treatment,” Thorpe said. “Getting that medical attention for early treatment is important.”