It is your twist and unjustifiable generalization of the author's words about the author himself:

> "aging is a synonym of cognitive decline"

compared to:

> As I near 60, I’ve come to realize I simply don’t have the same mental sharpness or stamina I used to.

The author did not say anything about anyone else.

Synoym: https://www.bennetyee.org/http_webster.cgi?isindex=synonym&m...