Bad news from scientific studies on baboons and health workers that shows chronic stress raises mortality rates for those who are at lower levels in a hierarchy much more than for those at the top. This despite the stress being tougher on those at the top. Jonah Lehrer details in the WSJ article "It's Good To Be The Top Banana".
I think there is a simple reason for this: if you're at the top the rewards from chronic stress are much greater than if you are at the bottom. The rewards make the difference in counteracting the negative influence of chronic stress. Unfortunately that'll be a tough premise to prove.