Some people who live to 100 and beyond smoke, drink hard liquor and down a beer every evening. Others indulge in daily ice cream or even drink three glasses of Dr. Pepper. This paradox is one reason several scientists who study extreme aging were not surprised by a recent study showing that longevity is roughly 50% genetic and 50% environmental ¡ª a substantially higher genetic contribution than earlier research indicated.

The take-home message isn¡¯t that your time on Earth is pre-ordained by your genes. A closer look beyond the headlines reveals something both more promising and more intriguing. For most of us, a healthy diet, regular exercise and adequate sleep can dramatically improve the chances of living a longer, healthier life.

Yet a small minority of people are born with a rare combination of genes that actually slows the aging process. These genes make them less susceptible to the usual age-related killers ¡ª heart disease, Alzheimer¡¯s and cancer ¡ª even when they don¡¯t consistently follow their doctors¡¯ advice.