Researchers from Imperial College London conducted a large-scale assessment to determine how a coronavirus infection, including what is commonly called COVID-19, may affect mental function over time. The results were documented in a peer‑reviewed medical journal, the New England Journal of Medicine, highlighting the potential long term cognitive consequences for a substantial portion of those who have contracted the disease.
Among the array of persistent effects attributed to the illness, brain fog stands out as a frequent and troubling symptom. Patients described challenges that resemble a clouded mind: trouble forming memories, difficulty sustaining focused attention, disrupted sleep, emotional changes such as sadness or irritability, and a notable rise in fatigue that makes simple tasks feel overwhelming. These experiences reflect a broader picture of how viral infection can ripple through neural networks and disrupt everyday cognitive performance, often lasting beyond the acute phase of the illness.
Quantitative analyses in the study suggest that, on average, a measurable decline in cognitive ability could occur, equating to a reduction of roughly six IQ points per year for affected individuals. The deficits identified spanned core cognitive domains, with particular impact observed in memory processes, the mental operations involved in planning and manipulating spatial information, and the verbal reasoning that underpins effective communication. While a six-point annual decrease may seem modest on a single user level, it carries greater significance when considered across the scale of the population affected by the infection, especially given the widespread reach of the virus and its potential to influence daily functioning for many over time.
To reach these conclusions, researchers analyzed data collected from more than a hundred thousand participants who completed an online instrument crafted to measure a range of cognitive abilities. The sheer size of the data set provided a robust view of how cognitive function shifts in the aftermath of infection and allowed scientists to identify patterns that might be obscured in smaller studies. The online tool included tasks designed to probe memory recall, attention control, processing speed, and problem‑solving capabilities, enabling a comprehensive profile of cognitive health in the post‑infection period.
The findings build on a growing body of work examining how SARS-CoV‑2 can influence brain health, aligning with prior observations about post‑acute sequelae of the disease. The study underscores the importance of monitoring cognitive function in people who have recovered from the acute illness and highlights the potential need for supportive strategies to mitigate functional impact. Health professionals may consider incorporating routine cognitive screening for at‑risk patients, along with rehabilitation approaches that target memory strategies, attention training, and sleep optimization to help individuals manage symptoms that interfere with work, study, and daily life.
While the research points to a population‑level concern, it also calls for nuanced interpretation at the individual level. A reduced IQ score by itself does not determine a person’s ability to lead a productive life, but sustained changes in cognitive function can influence educational achievement, job performance, and overall quality of life. The study emphasizes that vigilance, early recognition of symptoms, and access to cognitive support resources can make a meaningful difference in outcomes for those affected by the aftermath of COVID‑19. The findings are published in the New England Journal of Medicine, contributing to a growing, evidence‑based understanding of how viral infections may cast a long shadow over mental processes for many people in Canada, the United States, and beyond.