What about COVID in those who already have Alzheimer’s disease?

In a previous post I described recent research showing that patients with even mild COVID have shrinkage of several brain areas associated with olfaction and memory.  We don’t know yet if these changes to the brain will be permanent or if they will cause cognitive problems, but there is growing evidence that severe COVID requiring hospitalization is associated with a greater chance of persistent and even progressive cognitive deterioration. One recent study followed the cognitive function of 1438 COVID survivors 60 years of age and older who had required hospitalization for COVID in Wuhan, China.  All had been cognitively normal before getting COVID. One year after discharge from the hospital, over 12% had persistent cognitive impairment that in some cases was progressive. It is still unclear what causes persistent cognitive impairment in COVID.  Mild cognitive impairment, often called “brain fog,” is common even in mild COVID infections, but in most cases, cognition appears to return to normal.  What  causes the persistent and progressive cognitive issues? Rarely, the COVID virus gets into the brain and causes encephalitis, infection of the brain.  In one meta-analysis published last year, the incidence of encephalitis in COVID patients was only 0.215%, but 13.4% of these people died. There is some evidence that the protective blood brain barrier is breeched during COVID infections allowing toxins to enter the brain. There are several other theories. It clearly will take time to work this out, to fully understand what causes the persistent effects on the brain and what we can do to improve neurological outcomes.

What concerns me about COVID as a person living with Alzheimer’s disease is this. What would even a mild case of COVID do to my cognitive resilience? We already have evidence of brain atrophy in specific parts of the brain following mild COVID. It seems likely to me that those of us who have Alzheimer’s disease or other dementias will have less of a cognitive cushion to protect us from even a mild case of COVID. So far there has been no research that I can find that examines this issue.  Until that research is done, I am being very careful to limit my exposure to COVID. A little paranoid perhaps? I just want to keep my brain working as well as it can for as long as possible.