Even mild forms of COVID-19 can cause a reduction in brain size, according to scientists in the UK.

 

They scanned the brains of over 400 people who had previously had COVID-19, most of them mild cases.

 

They found that the overall brain size in infected participants had shrunk between 0.2 and 2 percent, and patients experienced losses in grey matter in the olfactory areas, linked to smell, and regions linked to memory.

 

The apparent effect of this was that those who had recently recovered from COVID-19 found it a bit harder to perform complex mental tasks.

 

The study was published on Monday in the science journal Nature. Lead author of the study Professor Gwenaelle Douaud, from Oxford University’s Wellcome Centre for Integrative Neuroimaging said: “We were looking at essentially mild infection, so to see that we could really see some differences in their brain and how much their brain had changed compared with those who had not been infected was quite a surprise.”

 

The study used biological information from a separate project, the UK Biobank, which has followed the health of 500,000 people for about 15 years and has a database of scans recorded before the pandemic — providing a unique opportunity to study the long-term health impacts of the virus.

 

Scientists also do not know whether there is any variation in the effect that COVID-19 variants have on the brain — the research was carried out when the original virus and alpha variant were most common.

 

Researchers also do not know yet whether these changes are permanent, but Douaud said: “We need to bear in mind that the brain is really plastic — by that we mean it can heal itself — so there is a really good chance that, over time, the harmful effects of infection will ease.”