- A neurologist credited as the world's oldest practicing doctor shared three longevity principles
- He emphasized keeping the mind active through learning, hobbies, and intellectual challenges
- He advised against carrying hatred, highlighting its harmful effects on mental and physical health
A neurologist once recognised by the Guinness World Records as the world's oldest practicing doctor shared three simple principles he believed helped him live a long, meaningful, and mentally active life. Before his death on December 22, 2025, at the age of 103, he reflected on these habits in an essay for CNBC Make It.
The doctor said people often asked how he managed to remain active, sharp, and fulfilled well into old age. While he acknowledged that genetics and luck play an important role in longevity, he believed daily habits and mindset also shape how people age physically and mentally.
Over the years, he narrowed his philosophy down to three practical rules.
Keep the mind active and engaged
He believed mental activity is essential for maintaining clarity and quality of life, comparing the brain to a muscle that weakens without regular use. Even in later life, he continued challenging himself intellectually. He enrolled in law school at 60 and passed the Ohio bar exam at 67.
According to him, staying mentally engaged does not necessarily mean pursuing a career. Reading, volunteering, learning new skills, playing an instrument, or taking up hobbies that encourage curiosity and thinking can all help keep the mind sharp.
"Work does not have to mean a job or career. It can mean volunteering, reading, learning a skill, playing music, joining a club or finding any activity that keeps your mind active. I have seen many people slow down once they stop engaging with the world. In my experience, staying mentally active is one of the best things you can do for yourself," he wrote.
Don't carry hatred
The neurologist also stressed the importance of emotional well-being. He said carrying anger, resentment, and hatred takes a physical and mental toll over time. "When people ask me about my longevity, most want to know about a secret diet or exercise. Diet and exercise matter, of course. But I also think your outlook on life matters," he said.
While disappointment, loss, and unfairness are unavoidable parts of life, he believed dwelling on bitterness only harms the person holding on to it. Chronic anger, he noted, can increase stress, raise blood pressure and negatively affect heart health.
He emphasised that moving forward does not mean excusing wrongdoing, but rather refusing to let negativity dominate one's life. Staying interested in people and focusing energy on meaningful experiences, he believed, contributes to a healthier and happier life. "You don't have to forget every wrong or excuse bad behavior. The point is to not let bitterness take over your life. I have always felt it is healthier to move forward, to stay interested in other people, and to focus your energy on the things that give life meaning," he added.
Enjoy everything in moderation
His final principle centered on balance rather than strict denial. He encouraged a sensible approach to food, lifestyle, and everyday pleasures, saying moderation makes enjoyment sustainable over the long term.
He often spoke about enjoying good food and drinks while also maintaining balance through vegetables, salads and healthy routines. In his view, extremes in any aspect of life can be harmful, while moderation supports long-term wellbeing.
"I enjoy a martini. I enjoy a good steak. My wife of 68 years, Sue, is a wonderful cook, and we always eat well. We also believe in having balance, plenty of salad, vegetables and moderation in all things. To me, moderation is what makes enjoyment possible over the long run. Have a sensible approach to what you eat. The same is true in many parts of life. Too much of anything can wear you down. Too little can do the same," he concluded.
The doctor's overall philosophy combined intellectual curiosity, emotional balance, and moderation.
