Biden supporters better look closely at his pick for Vice President because Sleepy Joe will be over 78 when he is sworn in (if he wins). Biden's physical health seems better than his mental health. When you watch him on stage the man is clearly "slipping" mentally. If he doesn't die in office, I wouldn't be surprised to see the 25th Amendment invoked because of his "dementia" or some inability to serve.
Sanders would be well over 79 years old, and just had a massive heart attack and refuses to release his medical records pertaining to his recent health. Seems to me he has a damn good chance of croaking in office and his VP having to step up to the plate.
Trump will be (only) 74 years old at his 2nd inauguration (if he is reelected) but seems to be in good health.