More than half of long COVID patients experience severe cognitive slowing that does not appear to improve over time, according to new research.
Persistent cognitive slowing – defined as increased time to process information and respond to it – also increases the severity of this neurological symptom in these patients, according to the study published in eClinicalMedicine, part of The Lancet.
Most people with COVID feel better within a few days or weeks of their first symptoms and make a full recovery within 12 weeks. But for some people with the virus, symptoms can last longer, and can develop into long COVID, which is still being studied.
In the new study, 119 patients with long COVID were compared to two control groups, 75 no-COVID participants (healthy) and 63 no-long patients (who had COVID 12 weeks ago but weren't still experiencing it at the time of testing).
The study participants completed two short web-based cognitive tasks, Simple Reaction Time (SRT) and Number Vigilance Test (NVT).
Compared to healthy controls with an average reaction time of 0.34 seconds for the SRT test, long COVID patients responded significantly slower at a mean of 0.49 seconds. And after accounting for the effect of age, the mean reaction time for long COVID patients was also significantly slower than healthy people of the same age.
Compared to 4% of healthy controls, 53.5% of patients with long COVID experienced severe cognitive slowing, with findings replicated across two clinical samples in the UK and Germany.
Other factors or conditions like fatigue, depression, anxiety, sleep disturbance, and PTSD did not account for the extent of cognitive slowing in people with long COVID.
A significantly greater proportion of moderate-to-severely impaired cases were also identified in the long COVID group, compared to those recovered from COVID and those without it.
Log COVID patients with lower SRT scores reported significantly lower results in their mental health assessments, exhibited less restful sleep, and reported higher depressive tendencies.
Similarly, NVT estimates differed considerably between COVID survivors and long covid patients, with long COVID patients taking significantly longer to react. Those still with covid were also less vigilant to stimuli compared to healthy controls, with the accuracy of their vigilance declining over time.
For long COVID patients with normal response speeds, they reported feeling significantly more tired than other participants with similar reaction times, suggesting they work harder to sustain their attention on demanding tasks.
No difference was found in cognitive slowing between long COVID patients who were hospitalised due to the virus, compared to non-hospitalised long COVID patients. Pre-existing psychological or neurological conditions like depression also didn't impact cognitive symptoms in long covid patients.
More research is needed on why and how there are cognitive deficits in long COVID patients.
Read more: Long COVID can actually rewire your brain, according to a new study (Yahoo Life UK, 7-min read)
Read more: Millions may have long COVID without realising it (Yahoo Life UK, 2-min read)
Read more: Long COVID: effects on fatigue and quality of life can be comparable to some cancers – new research (The Conversation, 4-min read)
Watch: 'The NHS sold out its staff': Doctors whose lives were devastated by long COVID to sue health service