Study reveals some brain changes, even in mild COVID-19

Adult COVID-19 survivors—even those with mild illness—who underwent scans showed changes in brain structure beyond that expected from normal aging, including in areas tied to smell and memory, according to a UK study published yesterday in Nature.University of Oxford investigators administered cognitive tests to and scanned the brains of 785 visitors to the UK Biobank imaging centers two times an average of 38 months apart.

Of the 785 participants, 401 (51%) were diagnosed as having COVID-19 between their scans, from March 2020 to April 2021. The remaining 384 participants were age- and sex-matched controls.

Patients were aged 51 to 81 years.Fifteen COVID-19 patients were hospitalized, and two received critical care. Relative to their nonhopsitalized peers, hospitalized patients were, on average, older and had higher blood pressure and weight and were more likely to have diabetes and to be men.Although previous research suggests that COVID-19 may cause brain abnormalities and cognitive dysfunction, most studies have involved hospitalized patients with severe illness and have been limited to post-COVID imaging data, the researchers noted. "To our knowledge, this is the first longitudinal imaging study of SARS-CoV-2 where participants were initially scanned before any had been infected," they wrote.Brain tissue damage, whole-brain shrinkageAmong COVID-19 survivors, an average of 141 days elapsed between diagnosis and the second brain scan.

Changes in these patients included a reduction in gray matter thickness in the orbitofrontal cortex (associated with sense of smell) and the parahippocampal gyrus (associated with memory of events).Scans also revealed evidence of brain-tissue damage in areas linked with the olfactory