The peer-reviewed research found significant changes to the areas of the brain that affect memory, smell and a reduction in brain size in people who caught the virus.
The authors say the documented effects were still seen after excluding the 15 people who had been hospitalised with COVID-19, implying even mild illness may have consequences for the brain.
From the available data the researchers also conclude that COVID-19 causes the shrinkage whereas being infected with the seasonal flu did not cause brain shrinkage.
The smell pathway and the memory pathway in the brain are connected and these are the same pathways affected in some dementias including Alzheimer's disease.