(Reuters). COVID-19, a compound that causes the brain to shrink and reduce the grey matter in areas controlling memory and emotion, can also cause damage to the smell-controlling regions of the brain, an Oxford University study found.

Researchers stated that COVID can cause severe side effects in some people. Additional research is required to see if these long-term effects could be reversed.

The researchers stated that there is “strong evidence” for COVID-19-related brain abnormalities. Their study was published Monday.

Even mild cases showed that participants experienced a decline in executive function, which allows for organisation and focus. On average, brain sizes decreased between 0.2% to 2%.

The peer-reviewed study, published in the Nature journal, investigated brain changes in 785 participants aged 51–81 whose brains were scanned twice, including 401 people who caught COVID between their two scans. On average, the second scan took 141 days to complete after the initial scan.

This study was done in Britain when the Alpha variant was predominant. It is not likely that it will include any infected by the Delta variant.

Some people with COVID were found to have brain fog, or mental cloudiness. This includes impairments in attention, concentration and speed of information processing.

Although the researchers didn’t say whether vaccination against COVID has any effect on the condition, the UK Health Security Agency stated last month that they had reviewed 15 studies and found that people who were vaccinated are about half the likely to experience long-term COVID symptoms than those who weren’t.