Covid and Alzheimer’s disease

One evening last week, I started coughing a bit.  I dismissed it as due to my persistent allergies. A few hours later I felt awful. I had a bad headache, shaking chills, and a temperature over 101 degrees. A home Covid-19 antigen test was immediately positive despite my having had all the recommended Covid vaccinations and boosters. For the next two days I coughed a lot, felt tired and confused at times, and my fever came and went. My breathing was fine. I didn’t have pneumonia.  I had mild Covid, and by the fourth day I felt almost back to normal.

One thing that hasn’t returned to normal yet is my sense of taste.  Covid infection can affect both the sense of smell (anosmia) and the sense of taste (ageusia). My sense of smell has been gone for over ten years due to my Alzheimer’s disease, but I have enjoyed almost normal taste.  Since the onset of my Covid infection, my sense of taste has been diminished and distorted.  Things that once tasted sweet now have no taste or taste sour. Chocolate no longer has an appealing taste. Orange juice just tastes sour and salty. Loss of smell and/or taste is common in people with Covid, occurring in about half of subjects, but it usually returns with time.

Another thing that hasn’t returned to normal yet is my cognitive ability. Yesterday I had to ask Lois what my phone number was.  I know it today, but I still am not as sharp as I want to be. The Covid virus easily enters the brain, even in mild cases. Neurological symptoms commonly include headache and mild cognitive impairment (Covid fog), but more severe neurological complications including ataxia and strokes have been reported. Interestingly, Covid infection appears to slightly increase the chance of getting Alzheimer’s disease in the year following the infection.  The effect is small, but it is most pronounced in women over 85 years old who are about 1.9 times more likely to be diagnosed with Alzheimer’s than those who did not have Covid (see table).

I could find surprisingly little information about the possible effects of Covid infection in those who already have Alzheimer’s disease. There are many papers looking at the deleterious effects of isolation during the early days of the pandemic, but there is almost nothing that addresses my most burning question: Are those of us who already have Alzheimer’s likely to have an acceleration of cognitive decline if we get sick with Covid? I would guess that the answer would be yes, but I haven’t found any high-quality studies that address the issue. I’ll keep looking and update this post if I find the answer.