"Lord, give me back my memory."

For months, as Marilyn Walters struggled to recover from Covid-19, she has repeated this prayer day and night.

Like other older adults who've become critically ill from the coronavirus, Walters, 65, describes what she calls "brain fog" — difficulty putting thoughts together, problems with concentration, the inability to remember what happened a short time before.

This sudden cognitive dysfunction is a common concern for seniors who've survived a serious bout of Covid-19.

"Many older patients are having trouble organizing themselves and planning what they need to do to get through the day," said Dr. Zijian Chen, medical director of the Center for Post-Covid Care at Mount Sinai Health System in New York City. "They're reporting that they've become more and more forgetful."