A new study published in the Journal of Psychiatric Research has found that many individuals who were hospitalized with COVID-19 continue to show signs of impaired attention up to three months after discharge. Even patients who had recovered physically and did not require intensive care showed measurable deficits in sustained attention and reaction time. While some cognitive recovery occurred over time, a substantial portion of patients still displayed signs of attentional dysfunction months later.
During the COVID-19 pandemic, a growing number of survivors began reporting persistent issues with memory, focus, and concentration—symptoms that often fall under the umbrella of “brain fog.” Researchers have attempted to better understand the cognitive consequences of infection, especially those related to attention, a core function that influences many aspects of daily life. Since attention underpins tasks ranging from driving to decision-making, identifying which aspects of attention are most affected—and how long those effects might last—has become a public health priority.
The study was led by a team of researchers in Brazil at the Federal University of the State of Rio de Janeiro, with contributions from institutions in the Netherlands, the United States, and Israel. Their goal was to determine whether hospitalized COVID-19 patients continued to experience attentional deficits after discharge, and whether these impairments persisted after three months—a time window often used to define the condition known as long COVID.
Their focus was on patients who had not been admitted to the intensive care unit and had recovered their physical functions at the time of hospital release. This allowed them to isolate the effects of COVID-19 itself rather than complications arising from more severe illness or invasive treatment.
To assess attention, the researchers used the Continuous Visual Attention Test, or CVAT. This 90-second computerized task requires individuals to respond as quickly as possible to certain shapes while ignoring others. It measures four specific subdomains of attention: focused attention (omission errors), response inhibition (commission errors), intrinsic alertness (mean reaction time), and sustained attention (variability in reaction time). Unlike many traditional neuropsychological tools, the CVAT is short, simple, and less affected by a person’s education level, making it especially useful in a clinical setting.
The study included 40 COVID-19 patients and 36 control participants who had not been infected with the virus. All COVID-19 patients had been hospitalized but did not need intensive care or experience delirium. The control group consisted of workers from a local healthcare facility who were screened to ensure they had not contracted COVID-19. Both groups were tested twice using the CVAT—once at baseline (for COVID-19 patients, this was the day of discharge) and again three months later.
The researchers also used a reference group of over 200 healthy individuals who had previously passed a national exam for driver fitness, which allowed the team to evaluate whether a person’s test performance was in the typical range.
At the time of discharge, COVID-19 patients showed worse performance than controls in three out of four CVAT measures: reaction time, variability in reaction time, and omission errors. These impairments reflected difficulties with alertness, sustained attention, and focused attention. The patients’ responses were slower and more inconsistent, and they were more likely to miss relevant targets during the test.
Commission errors, which indicate impulsive responding, were not significantly different between groups. This pattern suggests that the deficits were not related to difficulty inhibiting responses, but rather to problems staying focused and alert.
Three months later, the COVID-19 group showed signs of improvement. Reaction times and their variability had decreased, and omission errors were reduced as well. However, these gains did not return patients to the same level as the control group. On average, COVID-19 patients continued to show deficits in focused attention and intrinsic alertness compared to controls. Importantly, the control group’s performance remained stable across both testing sessions, ruling out the possibility that improvement among COVID-19 patients was simply due to familiarity with the test.
A closer look at the data revealed that 77% of COVID-19 patients had clinically significant impairments in at least one attention subdomain at the time of discharge. After three months, 40% still showed deficits. These rates were far higher than what was seen in the control group, suggesting that the impairments could not be explained by normal variation in the general population.
The CVAT scores were also compared to those of the reference group, which consisted of healthy individuals who were deemed mentally fit to drive. Using a statistical cut-off based on the 5th percentile of this reference group, the researchers found that 73% of COVID-19 patients fell below the threshold in at least one attention measure at discharge. This number dropped to 39.5% at follow-up, but it still represented a substantial portion of the sample. In contrast, very few controls scored below this threshold at either time point.
The most affected CVAT variable was sustained attention, measured by how much a person’s reaction times fluctuated during the test. This was followed by slower reaction times and increased omission errors. The researchers also calculated a measure called the coefficient of variability, which adjusts for baseline reaction time, and still found significant group differences. These findings indicate that the impairments in attention were not solely due to slower responses but also involved inconsistency in cognitive performance.
One implication of these findings is that people recovering from COVID-19—even those who seem physically well enough to go home—may not be cognitively ready to resume all daily activities. The researchers highlighted traffic safety in particular, noting that impairments in attention, reaction time, and focus are known risk factors for motor vehicle accidents. Tasks like driving, operating machinery, or making rapid decisions may be affected in ways that are not outwardly visible. While the study did not directly measure real-world outcomes like crash rates or workplace errors, the results suggest a need for caution and perhaps formal evaluation before individuals resume such activities after hospitalization.
The study has several strengths. By excluding patients with delirium, mechanical ventilation, or intensive care stays, the researchers were able to focus on a population that is often assumed to have fully recovered. The use of a short, accessible attention test like the CVAT also allowed for clear measurement of specific attention domains, minimizing confounding factors such as educational background or fatigue.
However, the researchers acknowledged limitations. The sample size was relatively small, which may limit generalizability. They also could not fully control for differences in educational level between groups, although statistical adjustments were made. Additionally, the study did not include neuroimaging or biomarker data, so the biological mechanisms underlying the attention deficits remain unclear. It is also unknown whether these impairments persist beyond the three-month window, or whether they are linked to other long-term symptoms like fatigue or depression.
Despite these limitations, the findings highlight the importance of cognitive assessments in COVID-19 recovery. A routine, short attention test like the CVAT could help clinicians identify individuals who may benefit from closer monitoring or cognitive rehabilitation. As the world continues to deal with the long-term impact of COVID-19, these kinds of tools could play a role in helping patients return to safe and functional daily living. Further research is needed to determine whether these attention deficits are temporary or part of a longer-term pattern of post-infection cognitive change.
The study, “Long-COVID-19 and Cognition: Persistent attention deficits after hospital discharge,” was authored by Aureo do Carmo Filho, Max Kopti Fakoury, Guilherme Janeiro Schmidt, Ana Lucia Taboada Gjorup, André Casarsa Marques, Júlio Cesar Tolentino Junior, Juliana Janeiro Schmidt, Andreza Maia, Eelco van Duinkerken, Kai-Uwe Lewandrowski, Kenneth Blum, and Sergio Luis Schmidt.