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Since the emergence of COVID-19, specialists have focused on the immediate effects it can cause: respiratory problems, body pain, fatigue, fever, or loss of taste and smell.

However, new research has revealed the importance of effects that can appear in the long term, specifically on neurological function. In this area of research, several studies have been conducted, focused on both adults and children.

A study published in Nature Medicine presented a comprehensive assessment of the postacute neurological sequelae of COVID one year after infection:

• The analysis covered a group of 154,068 people with COVID-19; 5,638,795 as a contemporary control group (part of the same group as the individuals with COVID); and 5,859,621 historical (previously treated) controls, all from the U.S. Department of Veterans Affairs national health care databases.
• The authors estimated the risks and burdens of incident neurological disorders at 12 months following acute SARS-CoV-2 infection. 
• The results showed that in the postacute phase of COVID-19 there was an increased risk of neurological sequelae, including: ischemic and hemorrhagic stroke, cognition and memory disorders, peripheral nervous system disorders, episodic disorders (such as migraines or seizures), extrapyramidal and movement disorders, mental health disorders, musculoskeletal disorders, sensory disorders, Guillain–Barré syndrome, and encephalitis or encephalopathy.
• Risks and burdens were elevated even in people who did not require hospitalization during the acute phase of COVID-19. 
• Few people in the study had been vaccinated against COVID, since vaccines were not yet widely available.
• The data presented are prior to Delta, Omicron, and other variants of COVID.

The authors noted that COVID-19 has contributed to more than 40 million new cases of neurological disorders worldwide. They also commented that these problems can be seen in previously healthy patients, regardless of age, sex, or race, as well as unhealthy habits such as smoking.

With regard to vaccination, it is worth mentioning an earlier study published in Nature Medicine by Ziyad Al-Aly, which found that vaccines slightly reduce, by approximately 20%, the risk of developing long-term brain disorders.

In another study, published in Brain by Myoung Hwa Lee, nine patients with COVID-19 who died during the initial wave of SARS-CoV-2 were evaluated by brain autopsy. The authors used immunohistochemistry to describe vascular pathology, neuroinflammatory changes, and humoral and cellular immune responses.

The researchers explored whether vascular damage could be associated with endothelial cell dysfunction. They also looked for the deposition of immunoglobulins to assess whether the compromise of endothelial cells may be an immune-mediated process.

The results showed that several large proteins, such as immunoglobulin M, which normally do not cross the blood-brain barrier, were present in the perivascular regions of deceased patients with COVID-19, which showed the loss of vascular integrity in these patients.

Another way of demonstrating the impact that COVID can have on neurological function is seen in the study by Gwenaëlle Douaud, which analyzed the same group of adults, using brain scans, before and during the pandemic:

• The group consisted of 785 adults aged 51-81 years, of whom 401 contracted COVID-19 at some point between the two scans. Almost all those who became ill (96%) had a mild case.
• The scans found a greater loss of tissue in specific areas of the brain related to olfaction and a reduction in overall brain size in those individuals who had contracted the disease.
• It was also observed that the group that became ill showed lower performance in various standardized tests of mental acuity.

Although most of this research has been focused on adults and older adults, neurological sequelae related to COVID are not limited to this age group, as evidenced by a study published in Morbidity and Mortality Weekly Report, which links COVID-19 to an increase in bacterial infections in children’s brains.

The authors of the various studies cited above agree that governments and health systems should develop policies, strategies, and plans for a post-COVID world that takes into account and addresses the prolonged effects that this disease can have on the brain.

NOTE: This story was produced using content from the original study and from other medical research, as well as health and public health sources, highlighted in related links throughout the article.