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People who had long COVID had a significant lag in how fast they responded on cognitive tests, according to a new report.

The study, published Jan. 25 in eClincialMedicine, evaluated 194 people with long COVID, which also is known as post-COVID-19 condition, or PCC. Study participants had one or more symptoms of long COVID at least 12 weeks after a confirmed COVID-19 diagnosis, and all were receiving care at a long COVID clinic in Germany.

The researchers also found the same thing when they assessed cognitive abilities in 76 people from the United Kingdom. The average ages of participants were in the late 40s.

The team compared both groups of people with long COVID to two control groups; one control group never had COVID-19, and the other group of controls had COVID-19 but didn’t show signs of long COVID.

All of the participants underwent computer-based cognitive testing that gauged their awareness of numbers and physical reaction time to a visual on the screen. Additionally, participants completed questionnaires about their health symptoms and mental health.

The average reaction time in the control group was 0.34 seconds, but people with long COVID (from both groups) had an average of 0.49 seconds. More than half of the participants with long COVID had response times that were slower than two standard deviations from the control mean, or average.

People who had long COVID and weren’t hospitalized for it had significant cognitive slowing compared with those who weren’t hospitalized for COVID and didn’t have long COVID, the authors wrote.

The investigators said that there wasn’t a significant link between mental health symptoms and long COVID. “Depression and sleep deprivation may increase reaction time. However, our findings indicate that mental health symptoms alone cannot fully account for the cognitive slowing in patients with PCC,” the authors stated in their report.

“The present study reported a significant psychomotor slowing in individuals diagnosed with PCC,” the authors said. “This might be an important factor contributing to some of the cognitive impairments reported in patients with PCC.”