Ask HN: Decreasing WPM After 40?

I have had a relatively stable typing speed of round 80-90 for at least 20 years but have noticed a recent sluggishness in keyboard performance after turning 40 (last year). I'm now at around 60-70. Do you any of you have similar experience of decreasing "performance" at the keyboard? Is this just age or could it be a sign of cognitive decline beyond what is to be considered normal? I'm thinking the effects of COVID could be subtle even in those who generally had a non-problematic infection..