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Over half of long COVID patients suffer persistent cognitive slowing, latest study reveals

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Over half of long COVID patients suffer persistent cognitive slowing, latest study reveals

In a recent study published in eClinicalMedicine, researchers determine whether the prevalence of considerable cognitive decline may very well be used as a diagnostic marker of long coronavirus disease 2019 (COVID-19).

Study: Long COVID is related to severe cognitive slowing: a multicentre cross-sectional study. Image Credit: PeopleImages.com – Yuri A / Shutterstock.com

What’s long COVID?

Because the emergence of the severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) at the tip of 2019, over 770 million individuals throughout the world have been infected, almost seven million of whom have succumbed to the disease.

Between 30-60% of COVID-19 survivors have reported experiencing persistent symptoms for weeks to months after recovering from SARS-CoV-2 infection, a condition that’s now commonly known as ‘long COVID.’ The World Health Organization (WHO) and United States Centers for Disease Control and Prevention (CDC) have defined long COVID as prior COVID-19 symptoms that persist or re-emerge inside three months of infection recovery or the event of latest symptoms that last for no less than two months.

‘Brain fog,’ a cognitive condition characterised by confusion, forgetfulness, lack of focus, and a general lack of mental clarity, is one of the vital common symptoms related to long COVID. Impairments in sustained attention capabilities, memory, and cognitive flexibility have also been reported with long COVID, with these symptoms often correlating with structural and functional brain changes.

No diagnostic tests are currently available for long COVID, thus leaving diagnosis to be based on self-reported patient evaluations. Moreover, there stays a vital need to obviously define and elucidate the danger aspects related to long COVID to support the event of future interventions to forestall and treat the disease.

Concerning the study

In the current study, researchers used a cohort of European participants to find out whether cognitive slowing was strongly related to long COVID. Importantly, ‘cognitive slowing’ was defined as increased time to process information and reply to it.

Chosen participants were divided into three cohorts, including those with self-reported long COVID (cases), the no-COVID group (healthy controls), and people with a history of prior COVID-19 but not long COVID.

The study participants accomplished two cognitive function tests, including the Easy Response Test (SRT), which involves using a spacebar to reply to monitor-presented visual cues and measure response time. In contrast, the Number Vigilance Test (NVT) measures sustained, long-term attentiveness by requiring participants to remain focused while being exposed to a protracted string of numbers with zero because the odd one out. Six questionnaires measuring mood and mental health, fatigue, sleep, trauma, and intelligence quotient (IQ) were also provided to the study participants.

Study findings

A complete of 194 individuals were included within the study, 119 of whom were diagnosed with long COVID, 63 of whom had COVID-19 but not long COVID, and 75 healthy controls. As in comparison with healthy controls with a median response time (RT) of 0.34 seconds for the SRT test, long COVID patients responded significantly slower at a mean of 0.49 seconds. After accounting for the effect of age, the mean RT for long COVID patients was significantly longer than age-matched healthy controls.

In comparison with 4% of healthy controls, 53.5% of long COVID patients experienced severe cognitive slowing. Likewise, a significantly greater proportion of moderate-to-severely impaired cases were identified within the long COVID group as in comparison with each COVID-19 survivors without long COVID and healthy controls.  

Long COVID patients with lower SRT test scores reported significantly lower ends in their mental health assessments, exhibited less restful sleep, and reported higher depressive tendencies. Much like SRT results, NVT estimates differed considerably between COVID-19 survivors and long COVID patients, with long COVID patients taking significantly longer to react to targets. Notably, RT on the NVT was strongly related to the slow RT observed in SRT, even when age and depression status was considered.

Throughout the NVT, long COVID patients were less vigilant to visual stimuli as in comparison with healthy controls, with the accuracy of their vigilance declining over time. Long COVID patients with normal response speeds reported feeling significantly more drained than other participants with similar RT, thus indicating that these individuals worked harder to sustain their attention on demanding tasks.

No difference was observed in cognitive slowing between long COVID patients who were hospitalized as a consequence of COVID-19 as in comparison with non-hospitalized long COVID patients. Thus, the severity of acute infection with SARS-CoV-2 doesn’t appear to find out the cognitive effects of long COVID. Likewise, the presence of pre-existing psychological or neurological conditions, equivalent to depression, didn’t impact cognitive symptoms in long COVID patients.

Conclusions

The present study reports significant cognitive slowing in 53% of long COVID patients that doesn’t appear to enhance over time. Quite, persistent cognitive slowing in long COVID patients was found to extend the severity of this neurological symptom in these patients.

There stays a ignorance on the mechanisms accountable for the cognitive deficits observed in long COVID patients. Due to this fact, additional research incorporating comprehensive neuropsychological assessments is required on a bigger and more diverse cohort of patients.

Journal reference:

  • Zhao, S., Martin, E. M., Reuken, P. A., et al. (2024). Long COVID is related to severe cognitive slowing: a multicentre cross-sectional study. eClinicalMedicine 68. doi:10.1016/j.eclinm.2024.102434.

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