After analyzing over six million people, study authors found people over the age of 65 who contracted COVID-19 were much more likely to develop Alzheimer’s within a year of their illness in comparison to a control group. Women over the age of 85 were the most at risk of experiencing severe cognitive decline.

More specifically, researchers say Alzheimer’s risk among older people nearly doubled (0.35% to 0.68%) over a one-year period post COVID-19 infection. As far as why this is happening, study authors can’t say at this time if COVID-19 triggers new Alzheimer’s cases or simply speeds up its onset.

“The factors that play into the development of Alzheimer’s disease have been poorly understood, but two pieces considered important are prior infections, especially viral infections, and inflammation,” says study co-author Pamela Davis, Distinguished University Professor and The Arline H. and Curtis F. Garvin Research Professor at the Case Western Reserve School of Medicine, in a university release.

“Since infection with SARS-CoV2 has been associated with central nervous systemabnormalities including inflammation, we wanted to test whether, even in the short term, COVID could lead to increased diagnoses.”

The wave of Alzheimer’s cases ‘will be substantial’

Researchers analyzed anonymous electronic health records encompassing 6.2 million American adults 65 and older who received medical treatment between February 2020 and May 2021. These participants also had no history or prior diagnosis of dementia.

Study authors then divided the individuals into two groups: one consisting of people who contracted COVID-19 during that period, and another featuring people who never had COVID. The coronavirus group included over 400,000 people, while the non-COVID group consisted of 5.8 million people.

“If this increase in new diagnoses of Alzheimer’s disease is sustained, the wave of patients with a disease currently without a cure will be substantial, and could further strain our long-term care resources,” Prof. Davis explains.

“Alzheimer’s disease is a serious and challenging disease, and we thought we had turned some of the tide on it by reducing general risk factors such as hypertension, heart disease, obesity and a sedentary lifestyle. Now, so many people in the U.S. have had COVID and the long-term consequences of COVID are still emerging. It is important to continue to monitor the impact of this disease on future disability.”

Corresponding author Rong Xu, a professor of Biomedical Informatics at the School of Medicine and director of the Center for AI in Drug Discovery, adds that study authors plan to continue researching the effects of COVID-19 on Alzheimer’s and other neurodegenerative disorders — especially when it comes to specific subgroups in the population that may be more vulnerable. They’ll also be looking at the potential to repurpose FDA-approved drugs to treat COVID-19’s long-term effects.