The research, published in the journal JAMA Network Open, found that nearly a quarter of COVID-19 patients experienced some issues with their memory.
While hospitalised patients were more likely to have such brain fog, some outpatients had cognitive impairment too.
People who have survived COVID-19 frequently complain of cognitive dysfunction, which has been described as brain fog.
Cognitive impairment that were found to be 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, they added.
The study was conducted from April 2020 to May 2021 and included 740 patients with no history of dementia. The average age of patients was 49.
Among all the patients, the researchers found that the most prominent deficits were in:
processing speed (18 percent)
executive functioning (16 percent)
phonemic fluency (15 percent)
category fluency (20 percent)
memory encoding (24 percent)
memory recall (23 percent)
The researchers noted that hospitalised patients were more likely to have impairments in attention, executive functioning, category fluency and memory.
While it is well-known that certain populations like older adults may be particularly susceptible to cognitive impairment after critical illness, however, in the relatively young cohort in the present study, a substantial proportion exhibited cognitive dysfunction several months after recovering from COVID-19.
The findings of this study are in line with research on other viruses like flu and early reports from COVID-19 patients, they said.
The authors noted the possibility for bias in the sample as some participants may have presented to Mount Sinai Health System because they were experiencing symptoms.
High levels of executive dysfunction following Covid-19 infection have considerable implications for long-term treatment, the researchers said.
Further studies are needed to assess the future impact of infection and to discover how the virus affects the brain, they said.