In 30 years, as Baby Boomers retire, there will be as many people over 80 as there are under 5. And there’s another disturbing trend: The number of students entering geriatric medicine is dropping. As America ages, who takes care of the grandparents? Guest: Dr. Jessica Colburn, chief resident at the Johns Hopkins Bayview Medical Center, is veering from the money-making path in medicine. She’s preparing to become a geriatrician.