Further work is necessary to monitor and develop understanding of recovery for individuals with ongoing COVID-19 symptoms.
Certain types of infection have previously been linked to cognitive impairment, including SARS-CoV-2, especially among patients experiencing long COVID-19; however, it is unclear whether these cognitive deficits can improve over time. To analyze whether these symptoms improve more than a year post infection, a study published in eClinicalMedicine performed 2 rounds of cognitive testing to conduct longitudinal tracking of cognitive performance and deficits up to 2 years after being infected with the virus.
Past studies have analyzed small, hospitalized cohorts during the first year of the pandemic (prior to vaccination) with somewhat short follow-up (approximately 6-12 months since infection). Further, few studies have used a longitudinal approach to assess the individuals’ cognitive trajectories and whether recovery can influence cognitive performance, according to the authors of the current study.
The United Kingdom COVID Symptom Study Biobank (CSSB) held 2 rounds of testing. Round 1 was conducted between July 12, 2021, and August 27, 2021, and round 2 between April 28, 2022, and June 21, 2022), to assess the effects of COVID-19 exposures on cognitive accuracy and reaction times. The virus’s presences, correlations, magnitude, and persistence of effects are relatively unexplored within community-based cases, according to the investigators.
There was a total of 3335 individuals who completed round 1, of whom 1768 had also completed round 2. Study participants were divided into 5 groups depending on their infection status and the associated symptom durations at the time of study invitation.
Case group 1 included individuals with positive SARS-CoV-2 test but no associated symptoms (asymptomatic COVID); case group 2 included individuals with positive SARS-CoV-2 test with between 1 and 13 days of associated symptoms; case group 3 included individuals with positive SARS-CoV-2 test and at least 28 days of associated symptoms (long COVID); control group 1 included individuals with negative SARS-CoV-2 test with at least 28 days of symptoms at the time of test (long non-COVID); and control group 2 (“healthy controls”) included individuals with negative SARS-CoV-2 test associated with 1-3 consecutive days of symptoms at the time of test with a low symptom burden (healthy non-COVID).
In both rounds 1 and 2 of assessment, participants completed 12 different cognitive tasks that assessed different cognitive domains, including working memory, attention, reasoning, and motor control, with a longitudinal analysis assessing change in performance between the 2 rounds. Effects of COVID-19 impairment on cognitive accuracy and reaction times were evaluated, as well as how ongoing symptoms after COVID-19 infection influenced self-perceived recovery.
The study results indicate that individuals with community-based SARS-CoV-2 infection present cognitive deficits in performance accuracy compared to their non-infected counterparts when among groups with a ≥12-week symptom duration following infection. Additionally, they presented no evidence that SARS-CoV-2 infection had impacted their reaction time when completing the cognitive tasks.
These individuals had self-reported as not being fully recovered. For those who had discernable deficits at initial testing, longitudinal follow-up indicated that the deficits persisted for nearly 2 years since infection.
Alternatively, the individuals who reported feeling recovered presented no impairment, including those who experienced long-term illness or symptoms. The findings are similar to a previous study that had reported higher cognitive performance for the 42 participants who self-reported being recovered compared to 117 who experienced ongoing symptoms. The recovery rate was highly correlated with the duration of symptoms, which showed a recovery rate of only 17% for those with ≥12-week symptom duration at 38 weeks since infection.
Limitations of the current study include potential selection and participation biases, findings were limited by the CSSB cohort composition, and data that would further contribute to the study were lacking (i.e., prior neurovascular and neurodegenerative comorbidities, cognitive assessment data prior to infection). Further, the study relied on participants voluntarily logging their symptoms and COVID-19 test results for the researchers to derive their infection status and duration of symptoms.
Cheetham N J, Penfold R, Giunchiglia V, et al. The effects of COVID-19 on cognitive performance in a community-based cohort: a COVID symptom study biobank prospective cohort study.eClinicalMedicine. Volume 0, Issue 0, 102086 https://doi.org/10.1016/j.eclinm.2023.102086