Compared to how much you can benefit from the exercise, the risk of falling and dying is really insignificant, to the point that I don't think it's worth debating between climbing and any other common form of exercise.
[EDIT]: Fix an incorrectly worded statement about expected value.
My uncle played football in high-school, broke his knee and it's bothered him ever since. He didn't die.
Everything we do has risk, and we shouldn't let it consume us. But I'd also not focus on death in isolation.
> the benefits of exercise massively outweigh the risks of even a dangerous activity like climbing.
In other words, the risks of heart attack, diabetes and other diseases are worse than rock climbing, even if you go climbing twice a week.
humbledrone, I doubt that's the choice most climbers are making. I'm also a frequent climber (mostly outdoors). If I could not climb, I would not be sedentary - I'd do something(s) else (I already do other activities, too). If I couldn't do anything other than take a stroll every day, I would do that, because I feel better when I move around. Most of the climbers I know are clearly this way - people who can't stand not to be active.
I am pretty convinced, myself, that I'd be better off walking for an hour on safe sidewalks every day instead of rock climbing. I think rock climbing, and other activities in which I partake, put me at higher risk for serious injury or death than a nice healthy walk. How much higher, I'm not sure.
But it's a free society (I live in the USA) and we can do what we want, so I climb, because I'm kind of addicted.
Given the direction that health insurance is taking, I do wonder if people who admit to participating in higher-risk sports will some day be penalized by higher premiums, as smokers are.
Things like that could easily make you more sedentary for the rest of your life.
I'm not sure about climbing, I just don't think the math is as easy as that :)
(a related issue that really annoys me is when they compare the dangers of ectasy and heroin using the death rate, when the quality of life destruction caused by ectasy is 1% compared to the horror that happens to a junkie)
It's hard to find statistics for indoor climbing, but for outdoor climbing there is a death for every 320,000 outings. If you go on two outings a week, your chance of dying is around 0.03% per year [1].
Getting the proper amount of exercise (compared to being sedentary), though, can decrease the total risk of year-over-year mortality by a factor of up to 4.5 times [2]. The overall risk of death for e.g. a middle-aged man is something like 0.2% [3], so any significant reduction to this factor compares very favorably with the risk of death from climbing.
So, basically, if your options are either a) be sedentary or b) get adequate exercise by rock climbing, it is better for your health to choose b. This comparison looks even better if you're doing only gym climbing (which is much safer than outdoor climbing).
[1] http://www.allclimbing.com/archive/2009/01/data-on-climbing-...
[2] http://circ.ahajournals.org/content/107/1/e2.full
[3] http://www.ssa.gov/oact/STATS/table4c6.html