There has been little discussion in popular media of Covid’s long-term effects on the brain. I wanted to share recent research from several learning and health institutions around the world that are beginning to tackle this problem.
It is important to note that this research is still in early stages.
An article published Jan. 5 in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association looked at decades of published scientific evidence to make a compelling case for COVID-19 expected long-term effects on the brain and nervous system.
Dementia researchers from The University of Texas Health Science Center at San Antonio (UT Health San Antonio) are the first and senior authors of the report and are joined by coauthors from the Alzheimer’s Association and Nottingham and Leicester universities in England.
“Since the flu pandemic of 1917 and 1918, many of the flulike diseases have been associated with brain disorders,” said lead author Gabriel A. de Erausquin, MD, PhD, Msc, professor of neurology in the Joe R. and Teresa Lozano Long School of Medicine at UT Health San Antonio. “Those respiratory viruses included H1N1 and SARS-CoV. The SARS-CoV-2 virus, which causes COVID-19, is also known to impact the brain and nervous system.”
The question is to what degree and under what form. Even mild COVID-19 infections may have negative effects on the brain long term, Dr. de Erausquin said.
Infiltrating the brain
The coronavirus is known to enter cells via receptors called ACE2. The highest concentration of ACE2 receptors is in the olfactory bulb, the brain structure involved in the sense of smell.
“The basic idea of our study is that some of the respiratory viruses have affinity for nervous system cells,” said senior author Sudha Seshadri, MD, professor of neurology in the Long School of Medicine at UT Health San Antonio and director of the Glenn Biggs Institute. “Olfactory 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 connects with the hippocampus, a brain structure primarily responsible for short-term memory.
“The trail of the virus, when it invades the brain, leads almost straight to the hippocampus,” Dr. de Erausquin said. “That is believed to be one of the sources of the cognitive impairment observed in COVID-19 patients. We suspect it may also be part of the reason why there will be an accelerated cognitive decline over time in susceptible individuals.”
The authors point out that:
Abnormal brain imaging that may be characterized by the appearance of lesions in different brain regions – and the appearance of other abnormal brain changes that may influence clinical presentation – has emerged as a major feature of COVID-19 from all parts of the world.
Abnormal imaging was seen in an individual whose only symptom was loss of smell.
The increasing evidence and understanding of SARS‐CoV‐2’s impact on the CNS raises key questions on the impact for risk of later life cognitive decline, and other dementia. This program of studies aims to better understand the long‐term consequences that may impact the brain, cognition, and functioning—including the underlying biology that may contribute to AD and other dementias.
The study will collect information over the next two to three years. Initial results are expected in early 2022 for the first set of evaluations. The consortium is aided by technical guidance from the World Health Organization.
Source: UT Health San Antonio Original Research: Closed access. “Chronic Neuropsychiatric Sequelae of COVID-19: the need for a prospective study of viral impact on brain functioning” by Gabriel A. de Erausquin, MD, PhD, Msc; Heather Snyder, PhD; María Carrillo, PhD; Akram A. Hosseini, MD, MRCP, PhD; Traolach S. Brugha, MD, FRCPsych, SFHEA; Sudha Seshadri, MD. Alzheimer’s & Dementia
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