By 1950 Kennedy was suffering almost constant lower-back aches and spasms. X-rays in the Travell records, which I examined with the help of a physician, show that the fourth lumbar vertebra had narrowed from 1.5 cm to 1.1 cm, indicating collapse in the bones supporting his spinal column. By March of 1951 there were clear compression fractures in his lower spine. He needed crutches to get up a flight of stairs. Later that year, during a trip to Japan, he had a severe crisis related to Addison's when he apparently neglected to take his steroid medications. He ran a temperature of 106°, and his doctors feared for his life. The episode convinced him to be more rigorous about taking his medicine, and over the next two years back problems became his principal complaint.You've got to marvel at the strength of JFK's will just to get through all this; it worked well enough that a bullet killed him before his body ever did.
And on top of all that, he still served in the Navy, even with his conditions. Compare that with the way our recent presidents and vice-presidents approached service in the military, and it seems like JFK came from another world.