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The overall risk of developing COVID-19 for people over the age of 65 remains low. Adene Sanchez/Getty Images
  • Researchers say people over 65 who’ve had COVID-19 have as much as an 80% higher risk of developing Alzheimer’s disease within a year.
  • Experts point out, however, that there is no evidence COVID-19 causes Alzheimer’s and the overall risk of developing Alzheimer’s within a year is still relatively low.
  • They note that even a small increase in Alzheimer’s cases could put a strain on the nation’s healthcare facilities.

Contracting COVID-19 when you’re over the age of 65 could put you at a substantially higher risk of being diagnosed with Alzheimer’s within a year.

That risk could be as much as 50% to 80% higher. The highest risk was found in women and people 85 years or older.

That’s the conclusion of a new study published in the Journal of Alzheimer’s Disease.

“Since infection with SARS-CoV-2 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,” said Dr. Pamela Davis, a study co-author and a professor at the Case Western Reserve University School of Medicine in Cleveland.

Researchers examined the records of more than 6 million people 65 and older who had medical treatment between February 2020 and May 2021. None had been diagnosed with Alzheimer’s at the start of the study.

Of the more than 400,000 who tested positive for COVID-19, their risk of developing Alzheimer’s within a year was 0.68%. That’s nearly twice the risk of 0.35% for those who did not develop COVID-19.

Dr. Santosh Kesari, a neurologist at Providence Saint John’s Health Center in California and the regional medical director for the Research Clinical Institute of Providence Southern California, says there is no evidence that COVID-19 causes Alzheimer’s.

“I want to be clear on that,” he told Healthline. “But this fits with what we understand about how inflammation can make things worse, including in the brain.”

“Alzheimer’s is a disease that develops over decades,” he said. “An infection like COVID or some other medical problem can push a person who’s on the edge of clinical dementia over to the point that it’s clinically apparent this person has a problem and needs more help.”

Heather Snyder, Ph.D., the vice president of medical and scientific relations at the Alzheimer’s Association, says there could be several explanations for the study results.

“First, the pandemic presented serious delays for individuals seeking out medical diagnoses like Alzheimer’s,” she told Healthline. “Meaning these results could be driven by those who already had Alzheimer’s when they were infected but had not yet sought out a formal diagnosis.”

“Alternately, COVID-19 infection, which is linked to immune changes including inflammation, may impact the onset of brain changes that are linked to Alzheimer’s and other dementia,” she added.

“However, because this study only showed an association through medical records, we cannot know what the underlying mechanisms driving this association are without more research” Snyder noted.

Kesari says it’s possible an earlier diagnosis would affect both the healthcare system and families.

“Patients, caregivers, families, the health system too,” he said. “It could affect finances as well as family support and family burden.”

“Some of these patients may have been at home doing OK. Now, instead of waiting another five years before they go to the nursing home, they’re going immediately because they’ve declined so much,” Kesari explained.

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

The study data was collected before the highly contagious Delta and Omicron variants were widely detected. Experts say it’s unknown how the strains might have impacted the outcomes of the study.

The number of people in the United States living with Alzheimer’s is growing quickly. According to the Alzheimer’s Association, an estimated 6 million Americans age 65 and older have Alzheimer’s. By 2050, that number is projected to rise to nearly 13 million.

The researchers said they will continue to examine the relationship between COVID-19 and dementia.

“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,” 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 the disease on future disability.

Meanwhile, experts say it is important for those who are most vulnerable to follow public health guidelines, especially when it comes to vaccines.

“If you vaccinate everyone, you would not get the bad COVID that could push you over into dementia, if you were on the edge,” Kesari said. “And if they get COVID, we have to use what we’ve learned about the drugs that can mitigate the inflammation.”

Snyder agrees with the prevention message.

“While we work to further understand the lasting impacts of COVID-19 on the brain, the takeaway message for protecting your cognition is simple: follow public health recommendations,” she said.

“If you have had COVID-19, it doesn’t mean you’re going to get dementia,” Snyder added. “But if you have had COVID-19 and are experiencing long-term symptoms, including cognitive difficulties, talk to your doctor.”