A variety of blood tests can also help point to some causes of cognitive impairment, such as sleep apnea, vitamin B deficiency or other hormone and thyroid issues, said Dr. Joanna Hellmuth, a neurologist at the University of California, San Francisco. But because brain fog can present in so many different ways, and because it has so many different causes, the diagnostic tests have their limitations, she added.
Sometimes brain fog may be hard to diagnose because it is caused by several different factors, even for a patient who has one overarching condition. Someone with lupus or multiple sclerosis, for example, may experience cognitive impairment because of direct damage to their brain cells — but they also may not be getting enough sleep, could have extensive fatigue or be on medications that contribute to brain fog.
Unlike with lupus and multiple sclerosis, direct damage to brain cells is much rarer in Covid-19. But some patients’ brains show dysregulation in their endothelial cells, which line blood vessels in the brain. This can lead to a more permeable blood-brain barrier that allows harmful substances through to the brain and changes cognitive function, Dr. Hellmuth said.
Researchers are finding that a more common cause of brain fog in Covid patients, as well as those who have been infected with other viruses like H.I.V. and Ebola, and even people who undergo chemotherapy for cancer, is inflammation — a steep and unwarranted increase in immune-cell activity that can wreak havoc — in the brain and the body. Studies show that patients with persistent cognitive impairment after Covid-19 have high levels of inflammatory markers in their blood and cerebrospinal fluid. “We’re just seeing a new virus creating the same old problem,” said Dr. Avindra Nath, the clinical director at the National Institute of Neurological Disorders and Stroke.
How do you clear up brain fog?
Even if doctors can’t find a physical cause for your brain fog, there are steps you can take to manage it, Dr. Hellmuth said. Start with short-term adaptive strategies to manage everyday tasks. Write notes and set alarms so that you don’t miss appointments. Take regular breaks during long projects so you’re better able to maintain focus and finish tasks. You might also try tracking your daily activities, using an app on your phone or just a notebook to figure out what times of day you feel most energetic and clearheaded. Then, reserve this time to do more difficult or complicated tasks.
Your health care provider may also suggest making lifestyle changes to improve your overall health and energy. “We try to encourage cardiovascular exercise, a good diet, sleep and social activities that are known to be beneficial for the brain,” Dr. Hellmuth said.