A study published in the December issue of the British medical journal Heart looked at 52,600 people over three decades, and it found that those who ran more than 20 to 25 miles per week lived no longer than those who didn’t exercise at all. Another recent study also found that people who ran faster than 7 minutes and 30 seconds per mile when they exercised enjoyed no mortality advantage over couch potatoes. But in both studies, people who ran regularly, but at shorter distances and slower paces, lived longest.

via Is running bad for your heart? | NewsOK.com.

Yet another study that adds to the conflicting data we already have.  For the record, I no longer run for exercise.  But my excuse is OA.