Like many flu-like diseases, COVID-19 may be causing negative long-term effects on the brains of individuals who become infected with it, according to an article published Tuesday co-authored by San Antonio doctors. 

The article, published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, cites decades of scientific evidence suggesting it is very likely that COVID-19 will have long-term effects on the brains and nervous systems of its survivors. The Alzheimer’s Association is helping launch a study to better understand how COVID-19 could increase the risk of diseases such as Alzheimer’s and psychiatric illnesses, including depression. 

“Since the flu pandemic of 1917 and 1918, many of the flu-like diseases have been associated with brain disorders,” said lead author Dr. Gabriel de Erausquin, professor of neurology in the Joe R. and Teresa Lozano Long School of Medicine and an investigator with the Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases at UT Health San Antonio.

Such diseases include the swine flu, caused by the H1N1 virus, and COVID-19, caused by the SARS-CoV-2 virus, he said. 

He said research is needed but that chronic consequences of COVID-19 could impact many individuals’ quality of life and independence and it is likely that even mild infections will have some negative long-term effects on the brain.

“The under-recognized medical history of these viruses over the last century suggests a strong link to brain diseases that affect memory and behavior,” said Maria Carrillo, Alzheimer’s Association chief science officer and a co-author on the article. 

The study will consist of work from a consortium of scientific experts representing over 30 countries, according to a statement from UT Health. The Alzheimer’s Association, a Chicago-based nonprofit dedicated to Alzheimer’s care, support and research, is putting about $300,000 toward the initial funding, said Heather Snyder, its vice president of medical and scientific relations.

These experts will enroll study participants from a pool of millions of confirmed COVID-19 cases documented in hospitals worldwide. A second group will consist of people who are participating in other international COVID-19 studies. 

Participants will be evaluated at an initial appointment and again at six, nine, and 18 months. They will be tested on their cognition, behavior, and brain activity measured by magnetic resonance imaging.

“This type of very large consortium will allow us to study people in a number of different settings, with an enormous variation in the cultural and genetic background, to be able to make these comparisons and establish this impact or these effects,” de Erausquin said.

Proof that the virus affects the brain lies in the COVID-19 symptom of anosmia, or loss of smell, said consortium member Dr. Sudha Seshadri, professor of neurology in the Long School of Medicine at UT Health San Antonio, director of the Glenn Biggs Institute, and a senior author of Tuesday’s article.

“Some of the respiratory viruses [like COVID-19] have an affinity for nervous system cells,” Seshadri said. “Olfactory cells [our smell nerve cells] are very susceptible to viral invasion and are particularly targeted by SARS-CoV-2, and that’s why one of the prominent symptoms of COVID-19 is loss of smell.”

The olfactory bulb – the bundle of nerves that transmit smell information from the nose to the brain – connects with the hippocampus, a brain structure primarily responsible for short-term memory. The hippocampus also is one of the first areas to be affected by Alzheimer’s disease.

The path the SARS-CoV-2 virus takes when it invades the brain leads almost straight to the hippocampus, de Erausquin said. 

“That is believed to be one of the [reasons for] the cognitive impairment observed in COVID-19 patients,” he said. “We suspect it may also be part of the reason why there will be an accelerated cognitive decline over time in susceptible individuals.”

The study will look at questions such as how severe these effects are, if such viruses accelerate mental diseases, and more, de Erausquin said. 

The study, which has just launched, will collect information over the next two to three years. As an investigator in the study and consortium, de Erausquin said he expects the results will be interesting and potentially helpful to the medical community. Initial results are expected in early 2022 after the first set of evaluations.

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Lindsey Carnett

Lindsey Carnett covers the environment, science and utilities for the San Antonio Report.