In a recent study published within the Latest England Journal of Medicine, researchers assessed cognitive functioning amongst adults with various levels of persistence of coronavirus disease 2019 (COVID-19) attributable to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in England.

Their results suggest that COVID-19 is related to measurable cognitive deficits, which can persist in the long run.

Study: Cognition and Memory after Covid-19 in a Large Community Sample. Image Credit: Berit Kessler / Shutterstock

Background

The primary documented cases of ‘brain fog,’ with symptoms resembling poor memory, impaired concentration, and difficulty considering, emerged as early as 2020, indicating that COVID-19 could have long-term cognitive impacts.

Though the phenomenon is well-known, what’s lacking is information on how it might persist and which facets of cognitive functioning are most affected.

Concerning the study

On this study, researchers hypothesized that cognitive deficits after the onset of COVID-19 needs to be quantifiable and related to covariates related to illness severity and duration.

Their second hypothesis was that individuals with prolonged COVID-19 symptoms should show more observable memory and executive function impairment, including brain fog and poor memory.

They conducted a cohort-based study tracking the prevalence of SARS-CoV-2 infection amongst 3,099,386 individuals aged over 18 years. Of those, 800,000 people were invited to finish a cognitive assessment and follow-up survey.

To be included, they need to have received a positive result on a SARS-CoV-2 diagnostic test or suspected that that they had COVID-19 and experienced symptoms for 12 weeks or more. Moreover, unvaccinated individuals with SARS-CoV-2 immunoglobulin-G antibodies and other randomly chosen people from the complete sample were included.

The cognitive assessment tested immediate and spatial working memory, verbal analogical reasoning, two-dimensional mental manipulation, spatial planning, word definitions, delayed memory, and data sampling. For every domain, participants were scored on accuracy; secondary information was collected on varieties of errors and response times.

Individuals were categorized into six groups based on SARS-CoV-2 duration. The primary category included those that had never experienced an infection or had an unconfirmed one; all other categories required a positive test result.

People within the second category had asymptomatic infections, those within the third had short COVID-19 that resolved in 4 weeks or less, and people within the fourth had symptoms that resolved in lower than 12 weeks. To be within the fifth category, individuals had symptoms that persevered for greater than 12 weeks; those within the sixth had persistent symptoms continuing until the cognitive assessments.

Researchers assessed nonresponse bias to look at which aspects were related to accessing and completing the cognitive assessment. Linear regressions, factor evaluation, and propensity-score matching (PSM) were used to research the info. Sensitivity analyses were also conducted to check the validity and robustness of the outcomes.

Findings

Of the 800,000 people invited to participate, 34.6% accomplished the questionnaire, with 141,583 completing no less than one cognitive testing task and 112,964 completing all eight.

Amongst individuals infected with SARS-CoV-2 once, being infected earlier throughout the pandemic was related to greater decreases in the general cognitive rating in comparison with those infected later. Nevertheless, the gap narrowed after adjusting for the severity of the illness.

On average, individuals who were sick for longer, were hospitalized, or were infected early on within the pandemic had lower overall cognitive scores than those that had never had COVID-19.

Multivariate regression results indicated that folks infected throughout the initial stages (when the unique virus or alpha variant dominated) showed higher cognitive functioning decreases than those infected with the alpha or omicron variants.

Similarly, greater decreases were seen in individuals with persistent and unresolved symptoms in comparison with those that never had COVID-19 and amongst individuals who were hospitalized in comparison with those that weren’t.

The PSM evaluation showed similar trends; cognitive benefits were observed based on vaccination status, with individuals who received two or more doses performing best. There was, nevertheless, no significant difference based on which vaccine was taken.

Conclusions

This massive-sample community-based study suggests that COVID-19 could also be related to long-term and quantifiable cognitive deficits. Nevertheless, people infected with more moderen variants may experience more negligible effects on cognitive functioning.

This might be because earlier strains of SARS-CoV-2 were dominant at a time when effective treatments weren’t available, and the health system faced heavy burdens. Repeated infections don’t appear to have any effect, but vaccination (particularly two or more doses) may provide small cognitive benefits.

Limitations of this study include the potential for participant self-selection bias and reliance on self-reported data. Certain groups were overrepresented within the sample, including White individuals and ladies; younger people and certain underprivileged groups were underrepresented.

Further studies are required to supply information on the longer-term implications of those findings.