A Covid-19 affected patient about to undergo a CT scan.
Ludovic Marin / AFP
British researchers have investigated the effects of severe forms of Covid on the brain. Per this study from the University of Cambridge, persistent cognitive deficits were found, leading to an effect identical to aging from 50 to 70 years.
Atlantico: A UK study analyzed the effects of severe Covid on the brain. the rresults indicate that cognitive deficits persist† According to this study, what would be the concrete consequences?
André Nieoullon: Yes, the study by the team at the University of Cambridge, following the one from Oxford University published a few weeks ago, confirms that a significant percentage of people who have suffered from a severe form of COVID-19, especially those hospitalized have demonstrable cognitive impairment more than 6 months after infection. In the University of Cambridge study, the number of patients hospitalized with these cognitive impairments is at least around 30%. Studies show that cognitive impairment essentially results in complex clinical pictures, including generalized fatigue, a form of apathy that reflects a loss of motivation, difficulty concentrating, sleep disturbances, general anxiety or even some form of post-traumatic stress. More specifically, a form of mental confusion, with difficulty in “finding words”, so-called “short-term” memory impairment (immediate memory), dizziness and an inability to concentrate, represents a rather specific clinic of this type of infection. , which was suggested a few months ago by psychiatrists at the University of Toronto.
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Although hospitalized patients, and especially those who have suffered from the most severe forms requiring mechanical ventilation, are most affected by these long-term cognitive effects (30-45% of patients according to certain studies), these effects appear to are not limited to these patients, but that deficiencies, certainly less significantly, are also observable in about 15% of people affected by COVID-19, including a form that has not led to specific hospital care, and even more up to 25% according to an American study. In general, cognitive and mental health damage is certainly greater than has been measured in the general population to date.
What could, in the Covid, explain an effect identical to an aging of 50 to 70 years, as proposed by the study from the University of Cambridge?
The lasting decline in cognitive performance has in fact been compared to the “normal” physiological aging process, with the exception of dementia pathology, which according to some studies results in a decline in cognitive capacity with age, which occurs more in the last decades of life, schematic after 60 years, although many discussions nuance this claim. In any case, the cognitive impairment identified in patients who have suffered from severe forms of COVID-19 has been associated, in particular by researchers at the University of Oxford, in addition to the expected changes in the areas associated with smell, with some form of reduction in brain volume, limited but very real, of the brain regions involved in cognitive functions and in particular of the structures involved in the memorization process. In particular, this brain imaging work shows a reduction in the so-called “grey matter” regions, ie those containing neurons, on the order of 0.2% and up to 2% in a few months after illness, which is quite significant. is. Moreover, this is the main argument of the Cambridge teams to propose that the effects of COVID-19 on the brain are similar to premature aging since, physiologically, in the context of “normal” aging, not pathologically, the reduction of the thickness of these same brain regions involved in memorization (particularly the hippocampus) is in the order of 0.2 to 0.3% per year after 60 years. Therefore, the most significant reductions observed in these imaging studies are indeed correlated with aging on the order of at least a decade, as suggested by the referenced study.
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The mechanisms of these cerebral changes are less clear and, conventionally, the most common causes are related to the effects of COVID-19 on the brain: exacerbated inflammatory processes that can lead to encephalitis, immune response of the body, serious condition likely to potentiate brain inflammation. , reduction of cerebral oxygenation during the acute phase of disease likely to promote discrete, localized strokes (a number of studies have shown an effect of COVID-19 on the incidence of ischemic stroke), apart from a direct effect of virus infection. At this stage, however, nothing is certain, but the trace of inflammation remains most likely.
To what extent should these results be qualified?
If the relationship of this brain damage to COVID-19 is undeniable, the fact remains that in other infectious pathologies and especially in inflammatory damage of different origin, similar damage is observed and also results in similar behavioral effects. It is therefore likely that the clinical picture due to infection with COVID-19 does not show specific specificity, but reflects the non-specific cerebral response, especially to the inflammatory process.
In addition, as I have suggested, there is no consensus on the decline in cognitive abilities and mental health associated with aging, with some studies finding neither the age-related reduction in brain volume nor the impairment of cognitive abilities outside of pathology. And even, in certain studies, there is an improvement in verbal and arithmetic skills, probably related to experience gained with age… It is therefore necessary to be careful of generalizations that may prove offensive.
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What could be the long-term consequences of these effects on the brain of severe Covid?
A number of concerns have been raised about a possible increase in the incidence of neurodegenerative diseases in populations affected by the coronavirus pandemic. These speculative considerations are essentially based on the observation that an increased incidence of these neurological pathologies and in particular Parkinson’s disease has been observed as a result of the Spanish flu epidemic at the beginning of the last century. As a result, certain teams have hypothesized that in the long term, a population of patients who have suffered from a (severe) form of COVID-19 may develop one of the most common neurodegenerative diseases, namely some form of the disease. Alzheimer’s or Parkinson’s disease. At this stage, there is no indication that this is actually the case in the millions of people who have contracted the infection. But caution dictates that we must reassure the population and make progress that the worst is not the casenever sure!