This 100-year-old Ohio man is the world’s oldest practicing doctor — and says retirement is ‘the enemy’ of longevity. Here are his 3 top tips to live a long and happy life

Dr. Howard Tucker of Cleveland, Ohio, says meaningful work is the secret to longevity. Tucker was born in 1922 and received his medical degree from The Ohio State University in 1947. He practiced neurology for 75 years, earning the Guinness…