Does Hydration actually make a difference, or is it overhyped?

Hydration's evidence base for longevity is thinner and more mixed than commonly assumed, with the most direct test of the question returning a null result. Weighing the data: Hydration looks an early-stage, lower-priority area for now — the evidence is only emerging (30/100), and its estimated impact (12/100) is on the lower end too.