We are a culture which obsesses about the risks and benefits of just about everything (which in itself is probably a stress risk), particularly when it comes to human health and longevity. And we usually do it badly.
So, at the risk of feeding that obsession, here is some actual science (presented with the help of some very nice graphics):
“I hate when someone tells me that something is risky,” says David Spiegelhalter, a professor of risk assessment at the University of Cambridge. “Well, compared to what?”
To answer his own question, Spiegelhalter converted reams of statistical risk tables into a simple metric: a microlife—30 minutes. If you smoke two cigarettes, you lose 30 minutes of your life (top graphic). Exercise for 20 minutes, and you gain two units of microlife. Over time bad habits accelerate your aging, and good habits slow it down (bottom graphic). “That seems to resonate with people,” Spiegelhalter says. “No one likes to get older faster.”
This data caught my roving eye, to no ones surprise, because Spiegelhalter flags red meat and sitting, two topics which I have beaten to death featured (and, yes, I am still standing when I work). I will also be glad to show my wife the data regarding the beneficial effects of 1 serving of alcohol (and even if you have two servings, you make a net gain of 1/2 microlife–funny how I did that math so quickly).
Anyhow, how many microlives are you gaining or losing every day?
More on risk from Spiegelhalter in this TED Talk. It is very useful info to help me achieve my ambition of NOT having the last thought that goes through my mind be: “I am so stupid.”
Sadly, Spiegelhalter doesn’t have great news for cyclists (mostly because drivers are so dangerous, I suspect). But it is a very compelling way of looking at the world, and public policy and personal decisionmaking would be VERY different if we all thought about risk in such an analytical manner.:
The Earthist Chronicles 
Excellent post!