The New England Journal of Medicine posted two new studies highlighting the extensive effect of COVID-19 on cognitive health, specifically drops in IQ, adding further to existing evidence of how SARS-CoV-2 – the virus that causes COVID-19 can influence the brain's health. 

Ziyad Al-Aly is a physician-scientist who has focused on studying "long COVID" since early patient reports about the latter condition even before the term “long COVID” was created. He has attested before the US Senate as an expert witness on long COVID and has published broadly on this topic. In his article published on The Conversation on February 28, Al-Aly documented some of the most major studies up to date on how COVID-19 can impact brain health with the most recent one revealing drops in IQ.

As many people have reported experiencing severe brain fog since the COVID-19 pandemic, it is important to understand how this fogginess is defined scientifically before delving into the most recent discovery. 

It started with a brain fog

Brain fog, as defined by Al-Aly, is a conversational term representing a state of mental fatigue or lack of clarity and foginess that makes it hard to concentrate, remember things, and think clearly.

The well-known virus can also cause a bunch of other problems, from headaches, seizure disorders, strokes, and sleep problems, to tingling and paralysis of the nerves, as well as many mental health disorders, he added.

He further pointed out that much evidence has revealed how COVID-19 affects the brain, however, it is still unclear how the virus causes these effects and no treatments are available so far. 

Hello, drops of IQ

In the new study published by the New England Journal of Medicine, nearly 113,000 people previously infected by Covid-19, had their cognitive abilities like memory, planning, and spatial reasoning evaluated.

Deficits in memory and executive task performance, according to the researchers, were the most prevalent findings in the studied group.

They discovered that this diminishing was mostly visible in infected individuals during the early stages of the pandemic and when the delta and omicron variants were prevalent. Hence, the risk of cognitive deterioration did not lessen as the virus emerged from the ancestral strain to omicron, the physician-scientist said citing the research.

In the same study, he added, individuals who had "mild and resolved COVID-19" showcased cognitive decrease equivalent to a three-point loss of IQ. However, those with untreated persistent symptoms, such as people with constant shortness of breath or fatigue, had a six-point loss in IQ. The loss was even higher in individuals who were in the intensive care unit for COVID-19 reaching a nine-point loss in IQ. Thus, Al-Aly stated, reinfection with the virus resulted in an extra two-point loss in IQ, as compared to no reinfection.

The COVID expert noted that in general, the average IQ is about 100, and any IQ above 130 means that the individual is "highly gifted". In contrast, an IQ below 70 generally means that there exists a level of "intellectual disability that may require significant societal support."

Al-Aly, framing the findings, estimates that a three-point decrease in IQ would elevate the number of US adults with an IQ less than 70 from 4.7 million to 7.5 million an additional 2.8 million adults with a level of cognitive impairment needing significant societal support.

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In another study in the same issue of the New England Journal of Medicine, the scientist revealed, that a control group consisting of more than 100,000 Norwegians between March 2020 and April 2023, showed worse memory function "at several time points up to 36 months following a positive SARS-CoV-2 test."

What does the future hold?

Al-Aly believes that these studies combined indicate that COVID-19 "poses a serious risk to brain health," even in mild cases, adding that "the effects are now being revealed at the population level."

The expert COVID-19 scientist referenced another recent analysis of the US Current Population Survey. The latter reveals that after the initiation of the COVID-19 pandemic, an additional 1 million working-age Americans complained of having “serious difficulty” remembering, concentrating, or making decisions "than at any time in the preceding 15 years." What was more concerning for Al-Aly is that this was mostly reported by younger adults between the ages of 18 to 44.

Moreover, he stated that data from the European Union indicated a similar trend referring to a 2022 statistic of 15% of people in the EU reporting memory and concentration problems.

Ziyad Al-Aly believes that moving forward, "it will be critical to identify who is most at risk." He stressed that "a better understanding is also needed of how these trends might affect the educational attainment of children and young adults and the economic productivity of working-age adults." 

"And the extent to which these shifts will influence the epidemiology of dementia and Alzheimer’s disease is also not clear," the scientist emphasized. 

In his opinion, the expanding body of research now authenticates that COVID-19 "should be considered a virus with a significant impact on the brain,"  as the implications have vast effects, from individuals' cognitive struggles to the possible impact on populations and the economy.

He concluded his analysis by stating "Lifting the fog on the true causes behind these cognitive impairments, including brain fog, will require years if not decades of concerted efforts by researchers across the globe. And unfortunately, nearly everyone is a test case in this unprecedented global undertaking."

What are other studies documented by Al-Aly? 

He reported that large epidemiological analyses revealed that individuals who had COVID-19 were at an increased risk of cognitive deficits, such as memory problems.

Shrinkage of the brain volume and changes to its structures after infection were also indicated in imaging studies performed on people before and after being infected.

Another study of people "with mild to moderate COVID-19" presented "significant prolonged inflammation of the brain and changes that are commensurate with seven years of brain aging," he added.

Intense COVID-19 that needs hospitalization or intensive care can lead to cognitive defects and other brain damage that are equivalent to 20 years of aging, Al-Aly pointed out.

Laboratory experiments in human and mouse brain organoids designed to imitate changes in the human brain showcased that SARS-CoV-2 infection triggers the fusion of brain cells which according to the scientist, "effectively short-circuits brain electrical activity and compromises function."

Autopsy studies of people who had severe COVID-19 but passed away months later due to other causes indicated that the virus still existed in brain tissue. In his opinion, this evidences that in opposition to its name, SARS-CoV-2 is "not only a respiratory virus, but it can also enter the brain in some individuals." However, he stated, that "whether the persistence of the virus in brain tissue is driving some of the brain problems seen in people who have had COVID-19 is not yet clear."

Al-Aly added that some studies reveal that "even when the virus is mild and exclusively confined to the lungs," it can still trigger inflammation in the brain and impair brain cells’ ability to regenerate.

COVID-19 can also derange the blood-brain barrier, he added. The blood-brain barrier is the shield that protects the nervous system, which is the control and command center of our bodies. The virus, he stated, can cause it to be “leaky” as studies that referred to imaging in evaluating the brains of people hospitalized with COVID-19 showed deranged or leaky blood-brain barriers in those who had brain fog.

The final study mentioned by Al-Aly is a large preliminary analysis that collected data from 11 studies including almost 1 million people with COVID-19 and more than 6 million uninfected others. This analysis revealed that COVID-19 elevated the risk of developing new-onset dementia in people older than 60 years of age, he stated.