A recent study using electronic health records of more than 6 million Americans suggests that adults over 65 with a history of COVID-19 have a significantly higher risk of developing Alzheimer's disease. While the study adds to growing concerns about the correlation between coronavirus and brain function, it's limited and does not show COVID-19 directly causes Alzheimer's.

"There's bound to be some inaccuracy when you're simply using diagnostic codes from electronic health records for your data set," says Daniel Murman, MD, board-certified neurologist. "For example, some of those patients could have already been demonstrating signs of Alzheimer's prior to contracting COVID-19. COVID may have just brought more people to the doctor in recent years. We really don't know."

Nevertheless, Alzheimer's disease is undoubtedly on the rise. Approximately 6.5 million Americans over 65 have Alzheimer's or another form of dementia, and that number is projected to reach 12.7 million by 2050. Read on to learn more about how COVID-19 affects brain function and what to do if you're experiencing persistent memory loss.

How COVID-19 affects the brain

Several mechanisms occur during a viral infection, like COVID-19, that may be associated with neurological disorders. When viruses and microorganisms invade your body, they can attack your nervous system. This direct infection may generate an inflammatory response throughout your body that can affect brain function. 

Brain fog, or trouble concentrating, is a common long COVID-19 symptom and may persist for weeks. Other long COVID symptoms include cognitive troubles, fatigue and behavioral issues – all of which can be signs of conditions that mimic Alzheimer's. 

Additionally, people with a history of certain medical conditions usually have a tougher time with COVID-19. As a result, they may be more likely to develop complications, including neurological issues. In the end, though, we still don't know much about  how COVID-19 affects the body long term.

"There's increasing research suggesting that COVID-19 can have short-term effects on the brain, but more research needs to be done to determine the long-term effects," says Dr. Murman.

Alzheimer's disease causes and risk factors

The following factors may significantly increase your risk for Alzheimer's disease:

1. Age – Most individuals with Alzheimer's are 65 and older. After age 65, your risk of developing Alzheimer's doubles every five years. By 85, the risk reaches nearly one-third, according to the Alzheimer's Association.
2. Family history – If you have a family member with Alzheimer's, you may be more likely to develop the disease. The risk increases if you have more than one family member with the disease.
3. Heredity – Two categories of genes influence whether a person develops a disease: risk genes, which increase the risk of developing the disease, and deterministic genes, which cause the disease. Alzheimer's genes have been found in both categories.
4. History of head injury – There's a correlation between head injuries – like those caused by falling or contact sports – and future risk of dementia. 
5. Heart health – Some evidence links brain health to heart health since the brain is nourished by the body's blood vessels, and the heart is responsible for pumping blood through those vessels.
6. Overall health – Research suggests that strategies for living a healthy lifestyle, such as following a Mediterranean-based diet, exercising regularly and practicing stress management, may help keep your brain healthy.

"A healthy lifestyle makes you more resilient to many health problems, including neurological conditions," says Dr. Murman.

Early signs of Alzheimer's disease

The most common signs of Alzheimer's disease include:

• Memory loss that disrupts daily life
• Challenges planning or solving problems
• Difficulty completing familiar tasks
• Confusion with time or place
• Trouble understanding visual images and spatial relationships
• Problems speaking or writing
• Misplacing things 
• Decreased or poor judgment
• Withdrawal from work or social activities
• Changes in mood and behavior

If you're consistently experiencing any of the signs above, it's a good idea to schedule an appointment with your primary care provider. Your doctor may refer you to a neurologist or specialist who treats diseases of the brain. Neurologists sometimes diagnose Alzheimer's based on changes in behavior or responses to memory tests. They may also use diagnostic tests or brain imaging, such as MRI or CT scans, to look for structural changes. Either way, an early diagnosis can help you explore treatments that may provide relief and allow you to maintain a level of independence.