A bout of COVID-19, even a milder one, may raise the risk of having a seizure in the next six months, a large new study suggests.
Researchers found that of over 300,000 Americans who had suffered a case of COVID-19 or the flu, COVID sufferers were 55% more likely to be diagnosed with a seizure or epilepsy in the next six months.
And a deeper look showed that the increased risk was among people who were not hospitalized: Of those who dealt with COVID at home, just over 0.7% were later diagnosed with a first-time seizure or epilepsy. That compared with just under 0.5% of people who were sick at home with the flu.
The link between COVID-19 and seizures was also stronger among children than adults.
The absolute risks are small, stressed senior researcher Dr. Arjune Sen of the University of Oxford in the United Kingdom. And this type of study, he said, cannot get at the underlying reasons.
But the study, published online Nov. 16 in the journal Neurology, adds to the many that have arrived at similar conclusions: After COVID, people can face longer-term health problems.
For some, that means a new medical condition, such as diabetes or heart disease. Many others deal with the wide range of ongoing symptoms known as long COVID — including neurological issues like loss of smell, headaches, dizziness and "brain fog."
Given that, it's logical to ask whether seizure risk could be elevated post-COVID, said Wyatt Bensken, an adjunct assistant professor at Case Western Reserve University School of Medicine, in Cleveland.
Bensken, who wrote an editorial published with the study, said the findings raise a number of questions. One is: How do people fare in the long run when they have post-COVID seizures? Are many having a one-time seizure, or a short-term issue? How often will they go on to have a chronic seizure disorder?
In addition, Bensken said, "milder" COVID — illness that doesn't send people to the hospital — varies widely. Some people are knocked out for weeks, while others have standard cold symptoms.
It's not clear whether people with certain symptoms — like loss of smell or other neurological manifestations — might be at greater risk of seizure than others, Bensken noted.
For the study, Sen's team analyzed electronic health records from patients at 59 health care organizations, mainly in the United States. The investigators identified more than 150,000 people who had been diagnosed with COVID-19 between 2020 and May 31, 2021, and compared them with the same number of patients diagnosed with influenza.
The researchers matched the two groups to be similar as far as age, race and the prevalence of chronic health conditions like heart disease, diabetes, asthma and obesity.
Overall, COVID-19 patients were more likely to be diagnosed with a seizure within six months: nearly 0.8% were, versus 0.5% of flu patients. The same was true when it came to epilepsy, which is typically diagnosed after a person has had two or more seizures: 0.3% of COVID patients were diagnosed with epilepsy, versus 0.17% of flu patients.
When the researchers dug deeper, they found no clear difference in seizure rates among patients who had been hospitalized with either COVID or the flu. The difference was concentrated among non-hospitalized people.
It's unclear why, according to Sen.
"Our hypothesis is that if you have a severe enough infection, from either virus, you may be more likely to have seizures — as there may be metabolic disturbance, electrolyte imbalance, sleep deprivation and so forth," he said.
For people with less severe COVID, researchers speculate that seizures may involve some sort of inflammation-promoting immune system response in the weeks after their illness.
The timing of the seizures makes that plausible, according to Sen. Among non-hospitalized patients, seizure risk peaked 41 days post-infection, versus nine days among hospitalized patients.
COVID infection also had a stronger relationship with seizures in children than in adults. Of kids aged 16 and younger who'd had COVID, 1.3% were diagnosed with a seizure or epilepsy in the next six months, versus 0.7% of kids who'd had the flu.
Again, the researchers hypothesize, the immune response might be involved: Among kids, the seizure risk linked to COVID-19 peaked 50 days after infection.
"The absolute risks of seizure are low," Bensken said, "but it's important for people to remember that there are long-term risks from COVID."
The researchers did not have information on whether patients had been vaccinated against COVID-19, Sen said. So it's not clear how that might relate to seizure risk.
But both experts said the findings underscore the importance of people curbing their risk, and their children's risk, of COVID-19 — through vaccination, boosters and other measures.
The U.S. Centers for Disease Control and Prevention has more on post-COVID conditions.
SOURCES: Arjune Sen, MD, PhD, associate professor, Nuffield Department of Clinical Neurosciences, University of Oxford, U.K.; Wyatt P. Bensken, PhD, adjunct assistant professor, department of population and quantitative health sciences, Case Western Reserve University School of Medicine, Cleveland; Neurology, Nov. 16, 2022, online