The good news: running is associated with a 19% decrease in mortality over non-runners. Hurray!
The bad news: if you run a lot or really fast, those gains evaporate to the point where you are statistically just as likely to die as non-runners again.
individuals who ran six and seven miles per hour had a significant 21% and 27% lower risk of all-cause mortality, whereas those who ran eight or more miles per hour had a nonsignificant 7% lower risk of all-cause mortality
Running up to 20 miles per week was associated with a significantly reduced risk of death, with the largest benefit observed in those who ran between 10 to 15 miles weekly (HR 0.73; 95% CI 0.60-0.89). For those who ran 20 to 25 miles and more than 25 miles per week, however, there was a nonsignificant 10% and 5% reduction in all-cause mortality
What does this all mean? Maybe pushing yourself to new levels of performance excellence is fun and great for goal-setting, great to keep you motivated... but might not be doing your health any good!
I don't like to change my behaviour on a single study, but I'm glad they are at least looking at it. It will be interesting to see where this lands as they dig deeper - what accounts for the difference?