Jimmy Carter at Maranatha Baptist Church, Plains, Georgia, April 28. Photo: Paul Hennessy/NurPhoto via Getty Images
Why it matters: At 95 years old, Carter is the oldest living president. He has had a number of stints in the hospital recently and had a procedure last month to relieve pressure from his brain caused by bleeding from recent falls. In addition to the surgery, Carter was treated for a urinary tract infection earlier this month and suffered a pelvic fracture in October. In 2015, he was diagnosed with melanoma.