Clinical trial at UAB studying way to clear âbrain fogâ from COVID-19 (Source: Pexels) By WBRC Staff | February 23, 2021 at 5:23 PM CST - Updated February 23 at 5:26 PM BIRMINGHAM, Ala. (WBRC) - âBrain fogâ is what doctors call a change in cognitive function many COVID-19 patients experience as a long-term effect from the virus. The fog is marked by memory problems and a struggle to think clearly. A new clinical trial at the University of Alabama at Birmingham is testing a rehabilitation method to remedy the problem. A report on 120 patients in France, published in October 2020, found that more than a third had memory loss and 27 percent had cognitive difficulties months after recovering from COVID-19. In another study, a hospital network in Chicago reported that, among 509 patients, nearly a third experienced altered mental function; of these, 68 percent were unable to handle routine daily activities such as cooking or paying bills.