I was very young, but I remember my grandfather was very afraid to retire from the steel mill where he worked most of his life because those who retired tended to get cancer shortly after and die. Sure enough, a little over a year after his retirement, he got a cold that wouldn't go away, and was diagnosed with cancer and died not too long afterwards.

I've wondered for a long time (based entirely on anecdotal observations) whether some forms of cancer and other illnesses arise more quickly from sudden shifts in daily habit. Sometimes it actually does seem to me like the episode in the Simpsons where Mr. Burns thinks he is invincible.