Two studies presented at the 2021 Alzheimer’s Association International Conference (AAIC) in Denver suggest that COVID-19 may lead to cognitive impairment down the road — and that certain symptoms that persist after recovering from the infection may be associated with cognitive decline.
One study uncovered ties between persistent loss of smell after recovering from COVID-19 and cognitive decline. The other found that people whose physical and respiratory health suffered due to a bout of COVID-19 were more likely to have issues with cognition afterward.
“I think what we’re learning is that it’s quite possible that these COVID-19 infections are potentially having an impact on the brain in some way,” says Rebecca Edelmayer, PhD, who is the senior director of scientific engagement for the Alzheimer’s Association in Chicago. Edelmayer was not affiliated with either study.
“There are still a lot of questions about the cause and effect, whether this is a direct or indirect effect [of COVID-19], but what we’re starting to see is data that suggests that people may be having some long-term impact from COVID-19 infection,” Edelmayer adds.
RELATED: Brain Fog: A COVID-19 Symptom That May Linger
Persistent Loss of Smell Tied to Cognitive Impairment
In one study, researchers assessed 233 people who tested positive for SARS-CoV-2 (the virus that causes COVID-19) and 64 healthy participants who tested negative. All participants in the study were age 60 or older. Those who tested positive were studied for three to six months after recovering from the virus.
The study participants underwent testing of their cognition and olfactory function — or function related to their sense of smell.
The results of the study suggested that loss of smell was associated with persistent cognitive impairment among participants who recovered from the virus — and people with more severe loss of smell were more likely to have more severe cognitive impairment.
However, the researchers noted, the severity of olfactory dysfunction was not associated with how severe one’s bout of COVID-19 was.
“There is some suggestion that lack of smell could be a symptom of COVID-19 infection itself, but some people who experience COVID-19 without that symptom are having a persistent lack of smell afterward. So I think we have to learn more about what that symptom itself may imply in terms of the long-term impact of COVID-19 on the brain,” Edelmayer says.
RELATED: What to Do When COVID Kills Your Sense of Smell and Taste
COVID-19’s Lingering Effects on Lung Health (and What It Means for Cognition)
In a small, Greek study, researchers tested physical and mental function beginning with 32 people two months after they’d been hospitalized and recovered from mild to moderate COVID-19.
According to the study’s lead author, George Vavougios, MD, PhD, who is a postdoctoral researcher for the University of Thessaly, the number of participants in this study has now grown to almost 100.
None of the participants had any prior coexisting health conditions other than hypertension, or high blood pressure.
Testing included the six-minute walk test, which measures how far someone can walk for six minutes, as well as their oxygen saturation — or levels of oxygen in their blood as they were completing the test. Other tests such as the Montreal Cognitive Assessment measured whether participants had experienced cognitive decline after recovering from COVID-19.
Early findings from the study showed that more than half (56.2 percent) of participants had cognitive decline after recovering from COVID-19. Cognitive decline was found to be most common among people who demonstrated poor physical health and had concerningly low levels of oxygen in the blood during the six-minute walk test.
“For a healthy person, oxygen saturation would be at 99 percent whether we’re exercising or walking,” he explains. But for many people in the study, their oxygen saturation dropped to 95 percent, which, Dr. Vavougios says, resembles the lung function of someone with COPD (a group of lung conditions that inhibit airflow and cause breathing issues).
This finding could spell trouble for brain health, explains Vavougios. “A brain deprived of oxygen is not healthy, and persistent deprivation may very well contribute to cognitive difficulties,” he said in a press release.
Another troubling finding was how the lingering effects of COVID-19 have affected participants’ ability to get back to their normal routines. According to Vavougios, people who were highly functional before COVID-19 have had to significantly reduce their work hours because of lingering health consequences caused by COVID-19.
“These people did not have their life or functionality back, and some of them even said so,” Vavougios explains. “It was subtle enough to escape clinical scrutiny, but it was not subtle enough to let them get back to work or their lives as they were before.”
RELATED: How to Stay Safe From COVID-19 When You’re Back in the Office
How to Protect Your Brain Health From COVID-19
What might these findings mean in the long run? “The general message would be not to underestimate even subtle changes in cognition [if you’ve had COVID-19],” warns Vavougios.
Edelmayer echoes this advice, adding that anyone concerned about their memory, cognitive abilities, or general health after recovering from COVID-19 should see their doctor for a thorough assessment.
Vavougios and Edelmayer agree: Much remains to be learned about the long-term effects of COVID-19 on the brain and the body in the long run. And as researchers work to understand this, Edelmayer emphasizes taking preventive measures against COVID-19.
“I think the simple take-home message is that people should really try to avoid getting COVID-19. It is a preventable disease at this point, and we do believe that the best way to do that is to get vaccinated and to follow precautions that have been suggested by the CDC and local public health agencies to further minimize the risk for getting COVID-19 until we can learn more,” she advises.