Covid and brain fog

The Quarantine Zone
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https://www.nejm.org/doi/full/10.1056/NEJMe2400189

A new study compares the cognitive functioning of people who didn’t get covid, those who had mild covid, serious covid, long covid, etc.

There are lots of findings, and, “The mechanisms of cognitive dysfunction after SARS-CoV-2 infection still need to be elucidated”. But it’s clear that covid does disrupt brain functioning in (usually small) but measurable ways.

Modest cognitive decline occurred with the original virus and with each viral variant, including B.1.1.529 (omicron). As compared with uninfected participants (control), cognitive deficit — commensurate with a 3-point loss in IQ — was evident even in participants who had had mild Covid-19 with resolved symptoms. Participants with unresolved persistent symptoms had the equivalent of a 6-point loss in IQ, and those who had been admitted to the intensive care unit had the equivalent of a 9-point loss in IQ. Of importance, these deficits were associated with many of the other symptoms that have been reported by persons with long Covid. The greatest deficits in cognitive function were associated with the original strain of the virus (before December 1, 2020) and the early B.1.1.7 (alpha) variant (from December 1, 2020, to April 30, 2021). Longer hospital stays and durations of acute illness were predictors of persistent global deficits. Memory, reasoning, and executive function (i.e., planning) tasks were the most sensitive indicators of impaired function, and scores on these tasks tended to correlate with brain fog. Vaccinations provided a small cognitive advantage. Reinfection contributed an additional loss in IQ of nearly 2 points, as compared with no reinfection.

I linked to the editorial item in the new England journal is medicine, which gives a very readable summary of the study and its results. But the editorial also links to the full study, if you want to read it. It is free to read, like much of the NEJM’s covid coverage.

https://www.nejm.org/doi/full/10.1056/NEJMoa2311330

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Here’s Eric Topol on this study. The part I find extra disturbing is that every reinfection is another 2 IQ point loss. I need my brain for my job, so I’ll keep trying to minimize my risk of infection.

With Covid running rampant in the rest of the population, I guess that means the Covid avoiders are getting smarter relatively.

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These numbers are averages, and my guess is that some people have noticable “brain fog” and others don’t, not that there’s a consistent small amount of damage. But that hard to tease out.

The new studies are consistent with a very early British study, that was actually set up as some kind of general cognitive study of the UK, but at the end of the study they asked a few questions about covid, which was then pretty new. (So only original variant.) It found that people who had had covid did worse on the cognitive test, with a clear “dose response” (those who’d been in the ICU did worse than those hospitalized, who did worse than those with confirmed covid, did worse than those with suspected covid, did worse than those who hadn’t had covid. This is back when tests were in short supply, so sicker people were more likely to be tested, as well as “tests positive” more likely to have had covid than "had covid-like symptoms.)

Google has gotten much worse at digging up medical studies, but I’ll see if i can find it.