Many Brain-aging study sample pools are from young folks that died in accidents, aged homeless alcoholics, and individuals that were in declining health.

Most cultures find it taboo to donate their beloved family members bodies for scientific dissection. Thus, people get ingrained "[bigotry] with extra steps" similar to phrenology proponents.

https://en.wikipedia.org/wiki/Simpson%27s_paradox

"Old age and treachery will always beat youth and exuberance" =3