TAMPA (WJW) — Some who recover from COVID-19 are experiencing memory loss and other cognitive problems known as “brain fog,” researchers found.

A study out of Mount Sinai Health System, which was published in the peer-reviewed JAMA Network medical journal Friday, showed that after looking at 740 COVID-19 patients, many had memory issues.

Participants were tested for memory encoding, which looks at how people can remember short-term pieces of information, and memory recall, which looks at how people pull up specific memories. About 24% of patients had trouble with encoding, while 23% had recall problems.

Those who were hospitalized were more likely to have “brain fog,” data revealed.

The study also showed participants were affected in the areas of attention, processing speed and a type of verbal fluency.

Another study out of Oxford University, published at the end of September, showed that more than a third of all people who contracted COVID experienced lingering side effects, including brain fog. Memory symptoms only applied to about 8% of their sample size.

But researchers of the new study were clear that more studies need to be done to learn more about the issue.

“The association of COVID-19 with executive functioning raises key questions regarding patients’ long-term treatment,” researchers said at the conclusion of the study. “Future studies are needed to identify the risk factors and mechanisms underlying cognitive dysfunction as well as options for rehabilitation.”

Read the full study here.