After falling ill with COVID-19, many people report having difficulty concentrating and remembering certain things, a condition of “brain fog” that lasts for several weeks and in the most difficult cases for months or years, without the possibility of resorting to particularly effective therapies to facilitate recovery. Mind fog is a well-known, often underestimated health problem that existed well before the coronavirus pandemic, but in the past two and a half years it has affected a growing number of people, prompting research groups to address it and deepen their scientific knowledge. .
According to various experts, mental fog (or “clouding of consciousness”) is part of the long list of “long COVID” symptoms, that is, the aftermath that coronavirus disease leaves in some people after recovery, even if they were not particularly ill . The symptoms reported by patients vary widely and range from a perennial feeling of tiredness to recurrent joint pain, through to taste and smell disturbances, headaches, vision problems and feelings of numbness in the limbs.
The mechanisms that lead the coronavirus to develop such persistent symptoms are not yet completely clear: research is ongoing and among the main suspects is the strong immune reaction induced by the viral infection, which leads our immune system to react more than due, damaging our body. The mental fog probably derives from the same phenomena, at least according to the research carried out so far.
Regardless of the cause, people with blurred consciousness usually have problems concentrating and doing many activities, including the most mundane ones. Patients struggle to find words while uttering a sentence, lose bits of conversation, quickly forget requests they have received, fail to pay attention to what they are doing, and sometimes feel absent or disoriented. Some compare their condition to that of having little sleep for many days, or to fatigue due to jet-lag (long plane ride and time zone change).
Defining precisely the boundaries of the mental fog is not easy and for this reason too precise medical definitions are lacking. Before the pandemic, the condition was found in people with severe sleep disorders, neurological diseases or in individuals returning from periods of severe work stress or with hormonal changes. The problem was also reported by patients taking drugs such as antihistamines or chemotherapy drugs.
In the years of the pandemic, cases of mind fog increased significantly and were reported by 20-30 percent of people who had had the coronavirus. Many of them reported having had it for a few weeks and then managed to recover, while others have had to deal with the ailments for months and some have not yet overcome them.
Living with this condition is not easy: some people still try to lead their life as they did before the illness, while others cannot work and find that they cannot find the concentration to do it as they did before they got sick. They seek help from doctors and specialists, but they are not always listened to as they would like and do not benefit from the recommended therapies, which mostly involve taking supplements and over-the-counter drugs.
It is difficult for doctors to identify not only the causes of mental fog, but also the most suitable treatments to help their patients recover. Tests that have long been available to assess mental conditions, and which usually require answers to quizzes and questions, are not suitable for diagnoses of blurred consciousness.
Among the most used tests to detect any mild cognitive impairment is the Montreal Cognitive Assessment, which consists of a series of tests on concentration, memory, language, calculation and orientation skills. It is a test used mainly to help neurologists in diagnosing senile dementia, therefore it is not very suitable for evaluating cognitive problems in younger subjects. Hardly a 55-year-old person does not pass the test, even if they have problems with clouding of consciousness, leading the examiner not to detect something strange.
In most cases, assessments are also carried out in the absence of a comparison with the patient’s condition before the disease, making it more difficult to identify any cognitive deficiencies developed due to the coronavirus. It can be normal in the tests, but with perhaps lower scores than those that would have been obtained by carrying out the same tests previously, before falling ill with COVID-19.
While tests do not always give reliable results, diagnostic tests may offer a few more elements to evaluate any changes in the physiology of the brain and the rest of the central nervous system. A research team from the University of Oxford (United Kingdom) compared the MRI scans of some volunteers who had taken the exam years before the pandemic, and who had then repeated it after having had the coronavirus. MRI is a non-invasive exam, which allows you to see the tissues inside the body, including those that make up the brain.
The comparison showed that, even in the presence of COVID-19 with mild symptoms, a reduction in the thickness of the tissues that form the brain can occur. In the most serious cases, the phenomenon was comparable to that which usually occurs over a period of ten years, due to the natural aging of the organism. The most significant reductions emerged in the areas of the brain involved in the management of memories and some executive functions. Many of the volunteers analyzed with this condition exhibited cognitive problems attributable to mental fog.
Instead of focusing on the effects, other research groups have dealt with the phenomena that cause the problem, finding a link between the violent immune response that our body can activate in the presence of the coronavirus and problems in the brain. One study in particular, published in July in the scientific journal Celloffered important new elements to try to explain the phenomenon.
The research was carried out under experimental conditions between the universities of Stanford and Yale in the United States, using a laboratory with a biosafety level 3 (BSL-3), such as to make tests carried out with active and contagious versions of the coronavirus safe. The research team had infected some mice with the coronavirus, then assessed the spread of the cytokines in the bloodstream and cerebrospinal fluid (the fluid around the brain) one week and then seven weeks after infection. Cytokines – together with chemokines – are mainly responsible for initiating the inflammatory process that leads to an increase in body temperature above the norm, on which viruses and bacteria are often calibrated to proliferate. They condition the inflammatory process and if they abound they can take it out of control, causing damage to the organism.
Analyzes on mice had revealed high levels of cytokines in the cerebrospinal fluid, which had contributed to increase the activity of microglia cells, which have among their functions that of identifying damaged neurons or external agents that could damage the central nervous system. . This hyperactivity induced by the high inflammatory state compromised the balance of the brain (cerebral homeostasis), making it less efficient. For example, the research team had noticed a loss of the sheaths that cover neurons, essential to ensure that the electrical impulses between these cells do not disperse.
The study had concerned mice and not humans, but it was nevertheless carried out by creating a model, that is, taking care to produce conditions that are comparable to those of our organism. High levels of inflammation are often present in patients with long COVID and similar mechanisms seen in the trial were also identified in the past in some patients undergoing chemotherapy.
Our brain is well protected and infectious agents rarely manage to sneak inside. This circumstance reinforces hypotheses about an indirect role of the coronavirus in causing brain problems, which can then lead to mental fog.
To the phenomena described by the US study, others are probably added, for example, to the damage caused by the coronavirus, always indirectly, to the walls of blood vessels and which can lead to the formation of small blood clots. These can clog the vessels, reducing the flow of oxygen to areas of the brain, without necessarily causing the death of neurons, but slowing down their functioning.
These hypotheses are much discussed in the scientific community and research is still ongoing, consequently new elements could emerge that contradict the analyzes carried out so far. However, there does not seem to be much doubt that mental fog is caused by multiple factors, some of which are already known and observed with other viral diseases, towards which we have however developed greater immune capabilities over time.
Although there have been great advances in the neurological field in recent decades, the functioning of the cells that make up our nervous system and how they interact and change over time are still partially unknown to us. Hence the difficulties in giving the right dimension to the problem of mental fog, as well as to several other ailments that existed before the pandemic. It is also not clear how reversible the damage caused by a coronavirus infection is, nor how long it takes for any recovery.
In the absence of specific therapies, neurologists advise their patients to try to sleep more, avoid unhealthy lifestyles, eat healthier foods, and experiment with relaxation and meditation techniques. People who show to have little of it are prescribed vitamin B, which is important for nervous processes, or are recommended to take specific medicines to control inflammation.
Some patients recover relatively quickly, feeling less and less fatigued and more present while doing things, for others the recovery is very slow and in the most severe cases the mental fog persists more than two years after the COVID-19 episode. Fearing the judgment of others or for work issues, there are those who prefer to ignore it and continue with normal activities, albeit making more effort and getting tired very quickly. In these cases, the lack of rest can worsen the situation, hindering recovery.
According to some research groups, the scientific evidence gathered so far on the causes and mechanisms that lead to clouding of consciousness indicate that this condition could be reversible, even long after the viral infection. The studies and experiments were in progress before the pandemic, for example to use some drugs in patients with cognitive disorders related to therapies with certain chemotherapy drugs. However, the research is still ongoing and the results of the experiments are uncertain.