The so-called “brain fog” symptom associated with long Covid is comparable to ageing 10 years, researchers have suggested. In a study by King’s College London, researchers investigated the impact of Covid-19 on memory and found cognitive impairment highest in individuals who had tested positive and had more than three months of symptoms. The study, published on Friday in a clinical journal published by The Lancet, also found the symptoms in affected individuals stretched to almost two years since initial infection. “The fact remains that two years on from their first infection, some people don’t feel fully recovered and their lives continue to be impacted by the long-term effects of the coronavirus,” said Claire Steves, a professor of ageing and health at King’s College. “We need more work to understand why this is the case and what can be done to help.” An estimated two million people living in the UK were experiencing self-reported long Covid – symptoms continuing for more than four weeks since infection – as of January 2023, according to the 2023 government census. Commonly reported symptoms included fatigue, difficulty concentrating, shortness of breath and muscle aches. The study included more than 5,100 participants from the Covid Symptom Study Biobank, recruited through a smartphone app. Through 12 cognitive tests measuring speed and accuracy, researchers examined working memory, attention, reasoning and motor controls between two periods of 2021 and 2022. In the first cohort of 3,335 participants during July and August 2021, researchers found lower cognitive scores in individuals with positive Covid-19 infections, with the largest deficits seen in those with more than 12 weeks of symptoms. The study said the deficits were comparable to the effect of “an increase in age of approximately 10 years, or exhibiting mild or moderate symptoms of psychological distress”. This, however, was smaller than other effects such as lower educational attainment or above-threshold fatigue levels, the study said. Researchers found no significant improvement scores in the second round of 1,786 participants in April and June of 2022, nine months after the first. The study found no cognitive impairment for individuals who reported full recovery from coronavirus, even among those who had symptoms for more than three months, which the study’s lead author, Dr Nathan Cheetham, described as “good news”. “This study shows the need to monitor those people whose brain function is most affected by Covid-19 to see how their cognitive symptoms continue to develop and provide support towards recovery,” Cheetham told PA news.