Following on from alcohol, we now have cat naps that are good for the heart but bad for "causing" diabetes.
http://news.bbc.co.uk/1/hi/scotland/glasgow_and_west/7931508.stm
http://news.bbc.co.uk/1/hi/health/6354855.stm
The first instance is probably getting cause and effect back to front: people who are likely to get type 2 diabetes are also more likely to cat nap during the day simply because they get tired more easily.
I remember one study that showed that the lifeline on the palm of one's hand really did appear to reflect one's life expectancy. Statisticians came to that conclusion by examining the palms of lots of dead people in mortuaries.
Sure enough, the older the person was when they died, the longer their lifeline was seen to be. Of course eventually it was realised that the older you get, the more wrinkles you have, including the length of the lifeline. It gets longer as you grow older. 
Hmmm, not good news for me - I love my afternoon 
and my father was diabetic so I definitely have a genetic disposition.
Just reading about it's made me tired - seeya later!
@ lifelines
As for the rest, yeah cause and effect a big muddled there. I have had periods in the past when I suffered from terrible insomnia and would fall asleep in the day (even standing up) for a few minutes at a time from exhaustion.
I'm pretty sure the need for a nap was the result there and not the cause of ill health.
Having a nap in the day limits the population sample to the unemployed and retired so that could also add to the causes.
There was another story about the size of your waist causing diabetes but I forget the numbers involved.
"The first instance is probably getting cause and effect back to front: people who are likely to get type 2 diabetes are also more likely to cat nap during the day simply because they get tired more easily."
Your conclusion sounds to be reasonable logic. Agreed. 
[Tiptoes out quietly, thereby allowing a sleeping Merry to nap... 
]