A new study has found that cognitive impairment can persist for months in COVID patients, even in those who were not hospitalized, according to CNN Health.

The study, published last week in the journal JAMA Network Open, found that nearly 25% of COVID patients in a Mount Sinai Health System experienced some memory issues. Hospitalized patients were more likely to have cognitive impairment after a COVID infection, but the study also found that some outpatients had it too.

Clinical neuropsychologist Jacqueline Becker and her colleagues, who conducted the study, wrote, “In this study, we found a relatively high frequency of cognitive impairment several months after patients contracted COVID-19. Impairments in executive functioning, processing speed, category fluency, memory encoding, and recall were predominant among hospitalized patients.”

“This pattern is consistent with early reports describing a dysexecutive syndrome after COVID-19 and has considerable implications for occupational, psychological, and functional outcomes,” the investigators wrote.

In a separate study, published in April in the journal Lancet Psychiatry, experts have found that at least 1 in 3 people with COVID had long-term mental health or neurological symptoms.

The U.S. Centers for Disease Control and Prevention (CDC) includes difficulty thinking or concentrating on its list of post-COVID conditions.

The agency says, “Although most people with COVID-19 get better within weeks of illness, some people experience post-COVID conditions. Post-COVID conditions are a wide range of new, returning, or ongoing health problems people can experience four or more weeks after first being infected with the virus that causes COVID-19.”

The new study noted that hospitalized COVID patients were more likely to have impairments in attention, executive functioning, category fluency and memory, according to CNN Health.

The researchers found 39% of hospitalized patients had memory impairment compared with 12% of outpatients.

They also noted the possibility for bias in the sample because patients came to Mount Sinai Health System because they were experiencing those neurological symptoms.

The authors wrote, “The association of COVID-19 with executive functioning raises key questions regarding patients’ long-term treatment. Future studies are needed to identify the risk factors and mechanisms underlying cognitive dysfunction as well as options for rehabilitation.” The story first appeared on CNN Health.