COVID-19 long-haulers are showing early signs of neurological disorders: at least 1 in 5 still report brain fog after months

• Around 1 in 5 coronavirus long-haulers still felt brain fog six months after their initial infection.
• That's according to a new preprint analysis that collected data from nearly 19,000 patients.
• Doctors will need to keep tracking long-haulers to know whether they have neurological disorders.

When people started reporting brain fog, dizziness, and vertigo following COVID-19 infections, doctors weren't sure how long the issues would last. Were these symptoms the short-term byproducts of a viral illness or early signs of a neurological disorder?

Now researchers are getting closer to an answer.

A new preprint analysis, which is still awaiting peer review, found that one in five coronavirus long-haulers - people who've been sick with COVID-19 for roughly three weeks or more - experienced cognitive impairment at least six months after their initial infection. For many patients, this brain fog has led to memory loss or difficulty concentrating or making decisions. In some cases, patients have had to take time off work or even file for unemployment.

"Neuropsychiatric symptoms appear to be a big part of the syndromes experienced by some people surviving COVID-19," Alasdair Rooney, a co-author of the analysis, told Insider.

Rooney's research pooled nearly 19,000 adult patients across 51 studies, making it one of the largest examinations of neurological symptoms among long-haulers to date. The patterns were the same whether or not the participants had been hospitalized and regardless of how severe their illness was at the start.

But without knowing how long these symptoms last, doctors can't yet classify them as neurological disorders, or even chronic illnesses. Data sets are complicated by the fact that different studies track long-haulers over varying periods of time, and from different starting points.

"Before you even get to the point of setting thresholds or a number of weeks after which you declare a chronic illness, you have to have agreements about where you're starting measuring from," Rooney said. "And in the studies we looked at, there isn't any at the moment."

Still, some evidence points to a potential link between COVID-19 and persistent neurological issues: A recent study found that 72% of coronavirus survivors who'd been diagnosed with brain disorders or damage first received those diagnoses within six months of their COVID-19 infection.

Insomnia and fatigue could be neurological issues, too

One of the challenges in diagnosing long-term COVID-19 symptoms is that doctors are still learning the underlying mechanisms of the virus itself. For instance, researchers haven't figured out why certain long-haulers develop fatigue, while others have chest pain or trouble breathing.

"It's almost like for long-haulers, there's this whole batch of symptoms and they reach their hand in and pull out a handful," Noah Greenspan, a physical therapist who runs a pulmonary rehabilitation center in New York City, previously told Insider. "For some people, it may be the gut. Some people, it may be the autonomic nervous system. Some people, it may be the lungs."

In addition to brain fog, 27% of coronavirus long-haulers in Rooney's analysis reported insomnia and 24% reported fatigue. Rooney said both symptoms can be rooted in neurological issues, but that's not the only possible cause.

"The reason we included fatigue was because we see it very commonly in the neuropsychiatric clinic," he said. "It's well recognized that in some people, fatigue has a physical cause and other people describe mental fatigue. And we don't know yet which it is."

Around of 19% of coronavirus patients in the analysis also reported anxiety, while 15% reported post-traumatic stress. Rooney said it's hard to know whether these issues were direct COVID-19 symptoms, simply related to the pandemic in general, or something else. But patients should take any persistent neurological or psychiatric problems seriously, he added.

"I would always advise them, if they were concerned about it, to ask advice - in other words, err on the side of caution and not minimize it," Rooney said.

Future studies should also consider the severity of these symptoms, he added, since brain fog may be life-altering for one person but merely inconvenient for another.

"What we need now is essentially much more research looking at these particular issues to understand: What are the limits of these symptoms?" Rooney said. "Are they functionally disabling or are they symptoms that people can live with?"