Early onset alzheimer's
Credit: Getty Images

The risk of being diagnosed with Alzheimer’s disease nearly doubles for older adults in the year following a bout with COVID-19, a new study of 6.2 million adults finds.

If this increase in new Alzheimer’s diagnoses continues to follow COVID-19 cases, the resulting wave of disease could further strain already limited long-term care resources, investigators said. Currently, 6.5 million Americans aged 65 years and older live with Alzheimer’s. And in 2020, 48% percent of nursing home residents had Alzheimer’s or other dementias, according to the Alzheimer’s Association.

Women at risk

In the study, investigators from Case Western Reserve University in Cleveland compared data on a United States population aged 65 years and older with and without COVID-19. After controlling for Alzheimer’s disease risk factors, people with COVID-19 were more likely to develop Alzheimer’s a year later. 

In the COVID-19 group, women aged 85 years and older were at highest risk, they found.

Infections and dementia

“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,” said co-author Pamela Davis, MD, PhD, in a statement.

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

Study participants received medical treatment between February 2020 and May 2021. They had no prior diagnosis of Alzheimer’s disease. The researchers controlled for factors such as age, other demographics, adverse socioeconomic determinants of health and comorbidities including hypertension, cardiovascular diseases and diabetes. 

Nursing home status

Notably, researchers did not control for nursing home stay status. While it is a risk factor for COVID-19, it is not a known risk factor for Alzheimer’s disease, first author Rong Xu, PhD, told McKnight’s Clinical Daily.

Clinicians have been optimistic that reducing general Alzheimer’s risk factors such as hypertension and heart disease would begin to make a dent in Alzheimer’s prevalence, Davis 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,” she said.

Study limitations include potential inaccuracies in Alzheimer’s disease diagnosis. This is not likely to affect the relative risk analyses, however, since all cohorts came from the same dataset, the researchers wrote. 

The investigators are planning longer-term follow-up and will also study COVID-19’s impact on other types of dementia, and which subpopulations may be more vulnerable, they said.

Full findings were published in the Journal of Alzheimer’s Disease.

Related articles:

COVID linked to high rates of lasting dementia, psychosis, large study finds

Pandemic research uncovers new links between COVID and cognitive decline