upshifter
n. A person who takes on a fast-paced, high-stress job after having previously retired or moved to a low-stress job.
Other Forms
Examples
2003
Christine retrained as a barrister and has been practising in East Anglian Chambers for almost a year. "It's nerve-racking work," she says, with glee. "I handle criminal cases, which are a big responsibility. I've just left court, and my hands are still shaking."

This is the kind of stress that upshifters seek, and it has actually been proven to be good for your health. Tests conducted by Jos Bosch of Ohio University show that a short burst of acute stress raises levels of immunoglobulins, the body's defence chemicals….

Cary Cooper, Professor of Organisational Psychology at Umist, believes that there is a definite upshifter "type". "They all have energy; they can't sit still, they talk fast," he says. "They have a bounce-back quality; they don't wallow in the negative." He also believes that events often push a person into a period of upshifting. "A critical moment will come along when factors coincide so people can alter their whole lives — divorce, redundancy, a death."
—Hermione Eyre, “A nerve-racking, stressful, exhausting life? Yes, please!,” The Independent, May 04, 2003
1999 (earliest)
So it seems likely that most people who buy Getting A Life will be upshifters. (How else could they afford it?)
—Roger Hutchinson, “The Good Life revisited,” The Scotsman, February 17, 1999
Notes
The radical idea contained in the first example citation isn't that some people are returning to high-stress jobs — many folks just have the need for speed and downshifting is probably the worst thing they could have done to themselves. No, the shocker is the claim that stress can be good for you. Doesn't that fly in the face of everything we've learned over the past 20 years about the effects of stress on the body, particularly the immune system? On the surface, yes, but the Ohio U. study mentioned in the cite makes a crucial distinction between "active stress" — such as meeting a deadline or racing to pick up the kids from school — and "passive stress" — such as watching horror flicks or TV war coverage. The researchers also differentiated between "acute stress" — intense but short-lived, such as handling an emergency at work — and "chronic stress" — less intense but longer-lasting, such as taking care of someone who is ill. Active or acute stress boosts the immune system (at least temporarily) while passive or chronic stress tears it down. As the researchers whimsically put it, "a hassle a day keeps the doctor away."