A few months after the beginning of the pandemic, scientists already warned that the virus can cause different sequelae and effects in the medium and long term, even after the most characteristic and immediate symptoms have ended; and, also, that although we often think of it as a purely respiratory infection it can cause damage of another nature, including neurological.
Now, research published in the specialized media JAMA Network Open delves into these theories by providing evidence about the occurrence of cognitive dysfunctions of different types in patients who have passed the covid, even long after the infection ends.
Measure neurological damage
The work in question is a cross-sectional study that analyzes data from 740 people during the period between April 2020 and May of this year, collected by the Mount Sinai Health System hospital registry. The participants, in any case older than 18 years, were on average 49 years old, spoke English or Spanish, had tested positive for the virus or antibodies, and had no history of dementia.
This cohort underwent different tests aimed at measuring various parameters of their cognitive performance , such as attention, working memory, processing speed, executive functioning, phonemic fluency, categorical fluency, memory coding, etc. memory retrieval and memory recognition.
Taking into account their age, educational level and gender , the deficit in these values was calculated, defining as such the scores in each test that were lower than the norms for each profile by at least 1.5 times the standard deviation. , in each case.
Through this method they detected that, on average, the participants showed deficits of 18% in processing speed, 16% in executive functioning, 15% in phonemic fluency, 20% in categorical fluency, 24% % in memory encoding and 23% in memory retrieval.
The negative effects on cognitive performance were more extreme in patients who had had to be hospitalized than in those who had not needed it, since they had a greater tendency to present deficits in attention, executive functioning, categorical fluency, and coding. memory and memory recall.
A high rate of brain fog and memory loss
Based on these results, the authors conclude that the frequency with which these cognitive deficits occur even several months after covid-19 is relatively high , something that was also maintained when possible confounders such as ethnicity, smoking, age were adjusted. body mass index, coincidence with depressive disorders and other comorbidities.
The parameters in which these people showed deficits show, as a whole, the reality of the incidence of disorders known as mental fog and memory loss in patients who have passed the SARS-CoV-2 infection; two phenomena that the literature already pointed to as probable consequences in the medium and long term.
In addition, and as the main author of the study Jacqueline H. Becker explains in an interview with the Health medium , most of the patients in whom these deficits were observed were ‘quite young’.
Why is covid causing these deficits
Be that as it may, both mental fog and memory loss would fall within the umbrella known as ‘post-covid’ or ‘long covid’, a group of conditions that a significant number of patients have been observed to develop after the disease.
The mechanisms behind it are unclear. Some authors have suggested that, in the case of neurological damage, it could be directly due to infection of the central nervous system by the virus. This hypothesis is based on the fact that this invasion has been observed in autopsies of covid patients; However, we must not lose sight of the fact that in these cases there is a very important bias when dealing with people who have not survived the disease.
Another theory is that neurological symptoms can stem from possible chronic inflammation that persists even after recovery. Finally, it is possible that they are manifestations of brain damage caused by the hypoxia suffered during the infection.
The further development for patients with these conditions is unclear. Although, as we have noted, Becker’s research finds high levels of neurological deficits after a mean of more than seven months, the authors believe that they are likely to dissipate over time in most patients.