One of the most important studies in the pandemic – studying the potential impact of Covid on the brain – was just published. The major findings of loss of gray matter, reduced brain size, and cognitive decline are concerning and need to be placed in context.
If you want to determine whether the SARS-CoV-2 virus can damage the brain, you would ideally have a MRI brain scan before and after the Covid infection and a matched (for age and sex, medical history) control group of people without infection who also had two sets of brain images. It just so happened that in the United Kingdom over tens of thousands of people enrolled in their UK Biobank had undergone a brain scan before the pandemic and a subset of these were brought back at an average three years later, with or without having had Covid. They also had basic cognitive testing – a connect-the-dots type of test – with their brain scans.
