At 103 years old, I’m the ‘world’s oldest doctor’: My 3 rules for a long, happy life are so simple—I tell it to 'all my patients'

Howard Tucker died on Dec. 22, 2025 at age 103, shortly after writing this essay for CNBC Make It. It is published here with his family’s permission.

I spent more than 75 years practicing as a neurologist, continuing until my hospital closed in 2022. Now, at 103 — and recently named the oldest doctor ever by Guinness World Records — people often ask how I stay happy, sharp and fulfilled.

I don’t believe there is one magic answer. Good genes and good luck certainly can give you a head start. But over the years, I’ve come to believe there are a few principles that matter a great deal.

These are my three non-negotiables for a long and meaningful life — they are simple, and pretty much anyone can follow them.

I tell all my patients that the mind is like any other muscle in the body: If you don’t use it, it weakens.