Photo/Illutration The Omicron subvariant of the novel coronavirus (Provided by the National Institute of Infectious Diseases)

Another long-term effect of the novel coronavirus appears to be a higher chance of patients contracting Alzheimer’s disease in the years to follow, according to the latest research. 

Numerous large research projects overseas have shown a link between COVID-19 and cognitive disorders, along with Alzheimer’s.

“The novel coronavirus is a new risk factor for dementia,” said Takayoshi Shimohata, a neurology professor at Gifu University, who also serves on the health ministry’s editorial committee that compiles a manual for treating COVID-19’s aftereffects. “There needs to be greater understanding that the illness also affects the brain.”

Doctors have warned about other possible symptoms from COVID-19 that could continue after the initial novel coronavirus infection, such as a shortness of breath, fatigue and losing the senses of smell and taste.

A September 2022 article published in the U.S. medical journal Nature Medicine reported on a study of about 150,000 Americans who tested positive for COVID-19.

The study found that people who were infected had a 2.03-fold risk of being diagnosed with Alzheimer’s a year after infection compared to those who were not infected. The risk of cognitive disorders was 1.77 times greater for those infected.

The British medical journal Lancet Psychiatry published an article in August 2022 that contained the results of an international study covering 1.28 million people. Those who were infected with COVID-19 continued to be at risk for dementia more than two years after infection.

Scientists have yet to pinpoint how the aftereffects can lead to cognitive disorders.

An article published in the January 2023 Nature Review journal laid out six possible factors, such as persistent infection, a reactivation of the virus within the patient’s body, the effect on the human intestinal flora and autoimmunity.

Researchers believe the most important factor is persistent infection. While the patient may test negative for COVID-19, those with a persistent infection may have a new virus reproducing in organs where the old virus lay hidden.

A study detected the RNA of the virus in the stool of patients seven months after they were diagnosed with COVID-19.

As for what causes dementia, one possibility may be nerve inflammation over a wide area of the brain. That, in turn, could lead to amyloid beta deposits, which is believed to be a cause of Alzheimer’s. The virus might also prevent the normal functioning of brain cells.

While there is currently no treatment for COVID-19’s long-term effects, research in the United States has found that those who have been vaccinated have a lower risk of having symptoms post-infection in comparison to those who have not had one shot.

“People should continue to get vaccinated to raise their bodily defenses and remain careful about not becoming infected,” Shimohata said.

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