Older COVID-19 survivors may be at a 69% higher risk of developing Alzheimer's disease within 1 year of infection, according to a retrospective study of 6 million Americans 65 years and older published yesterday in the Journal of Alzheimer's Disease.
The study, led by Case Western Reserve University researchers, involved analysis of the medical records of 6,245,282 adults aged 65 years and older who had medical visits but no previous diagnosis of Alzheimer's disease from February 2020 to May 2021. A total of 410,748 participants tested positive for COVID-19 during the study period, while 5,834,534 did not.
Ages 85 and older, women most at risk
COVID-19 survivors had a 69% higher risk of a new diagnosis of Alzheimer's disease within 1 year of infection than their uninfected peers (hazard ratio [HR], 1.69; 95% confidence interval [CI], 1.53 to 1.72). Participants aged 85 years and older and women were at particularly high risk (HRs, 1.89 [95% CI, 1.73 to 2.07] and 1.82 [95% CI, 1.69 to 1.97], respectively).
"Our findings call for research to understand the underlying mechanisms and for continuous surveillance of long-term impacts of COVID-19 on Alzheimer’s disease," the authors wrote.
The team said it's not clear whether COVID-19 triggers or accelerates development of Alzheimer's disease, noting that SARS-CoV-2 has been associated with inflammation and central nervous system disorders.
"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," coauthor Pamela Davis, MD, PhD, said in a Case Western press release.
More Alzheimer's could stress resources
Davis added that any increase in new-onset Alzheimer's disease translates to a higher number of older patients with an incurable disease could be substantial and may further strain the country's already stressed long-term care resources.
"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," she said. "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."
In the release, the researchers said they plan to continue studying the potential effects of COVID-19 on Alzheimer's and other neurodegenerative diseases and whether certain populations may be especially vulnerable to them. They also plan to assess whether any drugs currently approved by the US Food and Drug Administration could be repurposed to treat COVID-19's long-term effects.