Bill is aging so rapidly due to the stress induced by what he thinks Hillary will do to our country.
Hillary is doing so poorly, in part, because of his extramarital antics. She was probably expecting a nice easy run against Jeb! knowing that Jeb! wouldn’t bring the messiness up.
Now you’ve got Trump out there bringing it all up again and with Bill’s victims gravitating to him. Younger women are not only being exposed to Bill’s misogny, but Hillary’s enablement of it. And they’re turning in droves to Bernie because of it.
I bet Bill is getting regularly raked over the coals by Hillary about how he’s messed up her sure thing. Probably also living in fear of having another ashtray bounced off his forehead.
That sort of thing would cause rapid aging and age-related health issues.