There is famous and there is famous to the local community. Since all recruitment is local, meaning you have to go to a clinical site to enroll in a trial, the local community is the group of people who understand that your site is famous in Alzheimer's research.
And famous to the local community is precisely the goal of just about all recruitment now. You don't need to be Harvard or Yale. You don't even need to have a well known site PI. You just need to be famous to the small circle of people you are hoping will trust you. That could be your study coordinator or someone the local community already trusts.
By famous, I mean admired, trusted, given the benefit of the doubt.
Here's how to tell if you're famous: If I ask someone in your community to name the person who is known for X, will they name you? If I ask about which site or clinic is the best place, hands down, to get Y, will they name you?
Being famous to the local community is far more efficient than being famous to everyone. It takes focus, though.
It also means that you will always be there for the local community. People won't trust you if you come and go once your short-term recruitment goals have been met!
Invest in a person who will show up before they have to, who will help when they think no one is watching and who sees everyone as a vital community member - not just someone who looks like them. Trust comes from people and organizations that already do that in the local community.