Medical researchers have long been worried about the effects of the coronavirus on the brain and cognitive function.

Concern began when people often lost their sense of taste and smell after getting infected with the coronavirus. And since those senses involve brain cell and sensory links to the nose and tongue, it led researchers to the discovery that the coronavirus invades a structure called the olfactory bulb – which includes the brain cells that react to smell – to gain entry to the nervous system.

What’s more, extreme brain fog is also a common symptom of COVID-19 infection.

But whether these can make your brain more vulnerable to Alzheimer’s disease or other long-term cognitive problems is the million-dollar question researchers are trying to answer. So, let’s look at what they’ve found so far.

“Persistent lack of smell is associated with brain changes,” says researcher Gabriel de Erausquin, M.D., PhD, a neurologist with the University of Texas Health Science Center at San Antonio. “Once the virus has affected the olfactory bulb and caused effects there – changes that we can see with imaging – then other places in the brain that are connected to it also become abnormal, either in function or structure or both.”

What does this do to memory? Dr. de Erausquin and his team decided to find out.

They analyzed the brain health of 400 older people who had recovered from the coronavirus and found that 60 percent of these folks suffered some level of cognitive impairment.

The Texas researchers say they don’t know yet if these impairments, which included things like memory problems and difficulties with language, are likely to progress and get worse.1

But the research is just getting started.

Another investigation at the Cleveland Clinic has found a link between COVID-19’s impact on the brain and the development of Alzheimer’s disease.

Brain Changes Parallel Alzheimer’s Disease 

Cleveland Clinic scientists say that their investigation has identified physiological changes caused by COVID-19 that parallel the inflammatory changes that signal the development of Alzheimer’s disease and other types of dementia.2 What’s more, these changes are not necessarily connected to the coronavirus directly invading the brain.

“While some studies suggest that SARS-CoV-2 infects brain cells directly, others found no evidence of the virus in the brain,” says researcher Feixiong Cheng, PhD, who is with the Cleveland Clinic’s Genomic Medicine Institute. “Identifying how COVID-19 and neurological problems are linked will be critical for developing effective preventive and therapeutic strategies to address the surge in neurocognitive impairments that we expect to see in the near future.”

Dr. Cheng’s study used computer programs and artificial intelligence to unravel the similarities between the genetic changes and accumulation of proteins in the brains of COVID-19 sufferers with the changes in the brains of people who develop dementia.

“We discovered that SARS-CoV-2 infection significantly altered Alzheimer’s markers implicated in brain inflammation and that certain viral entry factors are highly expressed in cells in the blood-brain barrier,” says Dr. Cheng. “These findings indicate that the virus may impact several genes or pathways involved in neuroinflammation and brain microvascular injury, which could lead to Alzheimer’s disease-like cognitive impairment.”

They also found that people with the genetic allele APOE E4/E4, a genetic risk factor for Alzheimer’s, possess fewer active antiviral defense genes – and that makes them more likely to be infected with COVID-19.

This is important news for many of us with a family history of Alzheimer’s disease. Even if you don’t know for sure that you possess the APOE E4/E4 gene, I recommend taking all precautions to avoid infection with the COVID-19 virus.

If that wasn’t enough to cause concern, another study examined the cognitive function of patients hospitalized with the coronavirus and made a shocking discovery.

The Threat of Delirium 

A study at the University of Michigan demonstrates that among 150 patients hospitalized for COVID-19 infection near the beginning of the pandemic, more than 70 percent experienced delirium, an extreme state of mental disturbance involving confusion and agitation.3

In their study, the Michigan researchers found that the COVID-19 patients who developed delirium were sicker than other patients and had more comorbidities like diabetes and high blood pressure.

The researchers say a contributing factor to the cognitive effects of the coronavirus is the reduction of oxygen to the brain caused by the virus that can lead to blood clots and strokes. The study also showed a correlation between the use of sedatives and added delirium risk.

“It is common to use IV sedatives in the ICU, particularly for patients on a ventilator,” says researcher Phillip Vlisides, M.D., of the Department of Anesthesiology at Michigan Medicine. “However, from talking to nurses, we found that patients with severe COVID were inherently more delirious and agitated at baseline, perhaps prompting more sedative use.”

The study found that cognitive problems could persist even after people left the hospital. About a third of the patients still had delirium after being discharged and 40 percent of these patients continued to need skilled nursing care. For some of these people, the delirium lasted for months.

My Takeaway 

While these findings are far from definitive and leave us with more questions than answers about COVID-19’s role in Alzheimer’s disease development, there’s no doubt that infection with COVID-19 can lead to brain fog and other cognitive difficulties. This alone is concerning and is another important reason to ensure you’re doing everything you can to protect yourself against the coronavirus.

What’s more, try to reduce inflammation within your body using diet and exercise. Not only will this help strengthen your immune system against viruses of all kinds, but it will help protect your brain against memory loss.

As new information on COVID-19’s effects on the brain becomes available in the coming months I’ll let you know.


  1. https://alz.confex.com/alz/2021/meetingapp.cgi/Paper/57897 
  2. https://pubmed.ncbi.nlm.nih.gov/34108016/ 
  3. https://bmjopen.bmj.com/content/11/9/e050045 

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