The worse your case of Covid-19, the worse the 'brain fog' you are likely to suffer; disease has effect even in mild cases

Chart by The Economist shows levels of "brain fog" at different levels of Covid-19 seriousness.

Covid-19 is a new disease that is not fully understood, but new research by American and British scientists shows it causes problems with memory and concentration, often known as “brain fog,” even in mild cases.

The researchers teamed up with the BBC on the "Great British Intelligence Test," an online assessment billed to the public as a way to “test your cognitive strengths.” About 80,000 people "were asked to remember lists of numbers or locations on a chessboard to test their recall," The Economist reports. Other tests measured planning ability, verbal skills, problem-solving and the ability to manipulate information. "Questions about the virus, as well as about demographic factors such as age, ethnicity and socioeconomic status, were asked only after the test had ended."

The test showed that the more serious the disease, the greater the cognitive effect. "People ventilated for different respiratory diseases often face similar cognitive issues, but the performance of those with mild covid-19 symptoms suffered more than would be expected in the event of mild illness," The Economist reports. "Scientists are still unsure how exactly covid-19 is linked to cognitive impairment. . . . It remains unclear how long brain fog takes to clear, or if it does at all. That makes it difficult to estimate the lasting economic and social impact. And it reinforces worries that the health effects of Covid-19 will linger long after the pandemic is tamed."