"While Alzheimer's is primarily characterized by the harmful build-up of amyloid protein and tangles in the brain, there is also extensive inflammation in the brain that highlights the importance of the immune system in Alzheimer's. We have found that some of the same immune system changes can occur in both Alzheimer's disease and COVID-19," said lead author Dr. Dervis Salih, from UCL's Queen Square Institute of Neurology and UK Dementia Research Institute.
"In patients with severe COVID-19 infection, there can also be inflammatory changes in the brain. Here we have identified a gene that can contribute to an exaggerated immune response to increase risks of both Alzheimer's and COVID-19," Salih added, in the paper published in the journal Brain.
To understand the gene's link to Alzheimer's, the team sequenced genetic data from 2,547 people, half of whom had the brain disorder.
They found that people with a particular variation, called rs1131454, of the OAS1 gene, were more likely to have Alzheimer's disease, increasing carriers' baseline risk of Alzheimer's by an estimated 11-22 percent.
The new variant identified is common, and it has a bigger impact on Alzheimer's risk than several known risk genes, the researchers said.