Even mild COVID cases may be causing accelerated brain shrinkage, study says

Even mild cases of COVID-19 can cause brain shrinkage and an accelerated reduction of gray matter, a new study has found.

The study joins a growing body of evidence suggesting that even less severe cases of COVID-19 can affect the brain, though its authors and other experts said more research is needed to determine whether the impacts could be reversible or long-term – and it is unclear whether infection has significant effects on thinking, memory and other functions that affect quality of life.

The study, published Monday in the journal Nature, looked at brain scans of people before they contracted the coronavirus and in months after. It is the first of its kind to take a longitudinal approach, examining changes over time.

The 785 individuals who underwent two brain scans about three years apart were sourced through UK Biobank, a biomedical database in Britain. Among the group, 401 contracted the coronavirus, most of them mild cases that did not require hospitalization, between March 2020 and April 2021.

The people within the study ranged in age from 51 to 81. Of that group, those who were infected with the coronavirus had accelerated levels of gray matter loss compared with those who never tested positive.

The natural aging process results in the loss of gray matter every year, on average between 0.2% and 0.3%, according to researchers. But the study found that compared with uninfected participants, those who contracted COVID-19 – even those who had mild cases – lost between 0.2% and 2% more gray matter across several brain regions, including ones that are related to sense of smell: the parahippocampal gyrus and the orbitofrontal cortex.

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