Study Shows Sleep Apnea Increases the Risk of Developing Long COVID

New research published in Sleep on May 11 has shown that individuals with obstructive sleep apnea (OSA) may have up to a 75% greater risk of developing long COVID. The study analyzed the data of 1.8 million and 330,000 adults, all of whom tested positive for COVID-19 between March 2020 and February 2022. While the link between sleep apnea and long COVID did not seem to exist for children, adults with OSA were found to be far more likely to experience long COVID symptoms than those without OSA. In the larger data set of adults, those with OSA had up to a 75% greater risk of developing long COVID, while the smaller data set showed a 12% greater risk. The study's senior author, Lorna Thorpe, Ph.D., MPH, urged additional monitoring for individuals with sleep apnea who contract COVID-19, particularly women, who were found to be more susceptible to long COVID than men with the condition.

OSA is a common condition that affects approximately 29.4 million adults in the U.S. It is characterized by restricted breathing caused by a blocked upper airway, which results in poor sleep quality and low oxygen levels in the body. Long COVID is a relatively undefined condition that can persist for weeks to years and cause a range of symptoms, including fatigue, respiratory problems, and brain fog.

To gain insight into how long COVID and OSA are linked, Thorpe and her team analyzed data for over 2.2 million patients who had tested positive for COVID-19 in one of three data sets between March 2020 and February 2022. Of those patients, approximately 5% of adults and less than 2% of children had previously been diagnosed with OSA. Machine learning was used to identify patients who likely had long COVID based on follow-up symptoms and medical visits. The data sets showed that having OSA increased the likelihood of developing long COVID in adults, but not in children.

Thorpe pointed out that the variance in definitions of long COVID likely contributed to the discrepancy between the data sets in adults with OSA who developed long COVID. The study utilized both a stringent definition of long COVID and a broader definition, with the former finding a higher risk of developing long COVID in individuals with OSA. However, a broader definition produced a slightly lower risk. Given the variation in case definitions and dataset sizes, the exact risk of developing long COVID in individuals with OSA remains uncertain.

The study is part of the $1.15 billion National Institutes of Health RECOVER (Researching COVID to Enhance Recovery) program, which is investigating COVID-19 and long COVID.

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.

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.”

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.”