In-Depth: What an intelligence test reveals about COVID brain fog

Severe COVID linked to a 7-point drop in IQ
COVID brain fog measured on an intelligence test
Posted at 5:38 PM, Jul 28, 2021
and last updated 2021-07-29 11:48:46-04

SAN DIEGO (KGTV) -- A study using data from an online intelligence test offers new insight into the brain fog reported by so many COVID long haulers.

Months after infection, people who recovered from COVID scored lower than their peers on tests designed to measure memory, reasoning, and problem solving, according to a study published by The Lancet.

People who had the most severe symptoms had the largest declines. Those hospitalized and put on a ventilator had an average drop in cognitive scores equivalent to a 7-point decline in IQ, the researchers reported.

Previously hospitalized COVID patients who did not need a ventilator scored slightly better, but they still performed worse than individuals who reported having a stroke. Even people with only mild COVID symptoms had a small but measurable decline in thinking skills.

The study out of the UK examined data from 81,337 participants who took the Great British Intelligence Test in 2020. The researchers adjusted scores for factors like age, gender, education level, and income. Then they compared how people with COVID fared on the test.

The authors found declines in thinking skills up to nine months after infection.

The findings are in line with previous studies that have observed cognitive changes in up to 30 percent of COVID patients following a hospital stay and up to 80 percent of patients after a trip to the ICU, said Dr. Navaz Karanjia, the director of Neurocritical Care at UC San Diego Health.

Like the team in the UK, UC San Diego is currently studying the neurological effects of COVID and actively recruiting volunteers.

Dr. Karanjia said the UK study’s use of an “intelligence” test is somewhat misleading.

“Intelligence usually refers to what people think of one’s innate ability to think and it’s a permanent thing. It’s also a very culturally biased and loaded term,” she said. “I would not refer to what this study has found as a change in people’s intelligence at all.”

Instead, she said the findings have to do with long haulers’ ability to focus, multi-task and remember -- not really permanent changes in their IQ.

She also pushed back on the idea that severe COVID causes similar cognitive effects as a stroke.

“Stroke is an entirely different phenomenon. It causes part of the brain to actually die,” she said. “Because we don’t know whether the causes of these changes after COVID are biological or psychological, it is way too early to compare it to stroke. It could be much more reversible. It could completely improve over time.”

Researchers worldwide are still trying to figure out exactly how COVID affects the brain, but there are four likely factors.

Some viral particles could directly attack brain cells. Inflammation set off by the virus could affect blood flow or oxygen levels to the brain. The body’s own immune response might accidentally attack the brain. And the psychological burden from the disease and lack of sleep could cause a kind of PTSD.

Different mechanisms could be at play in different individuals, said neurologist Dr. Jennifer Graves, who is leading the UCSD study called NeuCOVID.

“The good news is we’ve been tracking these patients for many months now and the majority of patients, even if they worsen for a few weeks after their COVID infection, do tend to get better after three to six months period of time,” she said.

Once doctors pinpoint the mechanisms, they can come up with better treatments.

UCSD plans to study the neurological effects of COVID for the next ten years.