Doctors who specialize in gracefully aging and staving off frailty.
In terms of “return on investment in health outcomes for dollar spent” you could do much much worse than looking at geriatricians. Geriatrician’s are doctors who specialize in aging and keeping people not only healthy in their later years, but happy and satisfied with their lives. Simply seeing a geriatrician can reduce the likelihood death, depression, and key indicators of frailty (e.g. “falling”) down something like 40%.