People that suffered only mild COVID-19 still had memory and concentration problems, with some experiencing issues 9 months later, a study found

• People that had fully recovered from mild COVID-19 still had memory and concentration problems, study found.
• Cognitive performance can be affected for up to nine months, Oxford University researchers said.

People that fully recovered from mild COVID-19 still suffered from memory and concentration impairment – sometimes for up to nine months afterwards, a study has found.

The study by scientists at Oxford University found that a group of people who'd had mild illness and weren't complaining of ongoing COVID-19 symptoms performed worse in a nine-minute attention task than a group who hadn't caught the virus.

The post-COVID-19 group's memory of daily life – such as times and places of events – was impaired for up to six months, while attention impairment lasted for up to nine months, the study authors said in a press release Wednesday.

The study is the first of its kind, according to the researchers, to find deficits in sustained attention and memory of everyday events in those who'd had mild illness and had otherwise appeared to have fully recovered.

Most other cognitive tests, including working memory and planning, weren't affected, the study authors said. It means that cognitive deficits from COVID-19 could be wide-ranging – just as COVID-19 manifests itself as a spectrum of illness, ranging from no symptoms to fatal.

There is a "pressing need" to measure cognitive performance and better understand how the brain is affected by COVID-19, the study authors said.

Dr. Masud Husein, a professor of cognitive neurology at Oxford and study author, said that the underlying cause wasn't clear. But it was "very encouraging" that attention and memory deficits largely returned to normal in most people by six to nine months after infection, he said.

To get the results, the researchers ran a series of tests advertised to participants as "brain games". There were 53 people in the group who self-reported a previous mild COVID-19 infection, while there were 83 people in the group who said they hadn't caught the virus. None of the participants had received hospital treatment or had ongoing COVID-19 symptoms such as fatigue and brain fog, the study authors said. The average age of the participants was about 28, they said.

The study was published in Brain Communications, an open access journal. Its methods and findings haven't been formally scrutinized by other experts.

The researchers cautioned that the relatively small sample size and low numbers of participants older than 70 may mean the results aren't applicable to everybody.