How does resting heart rate affect longevity?

In a 16-year follow-up of 2,798 Danish men, those with a resting heart rate above 90 bpm had about three times the mortality of men below 50 bpm, after adjusting for fitness. A 2016 meta-analysis of 46 cohort studies found each extra 10 bpm at rest came with about 9% higher all-cause mortality. These are associations, and fitness explains part of them.

Source: Jensen et al. (2013), Heart; Zhang et al. (2016), CMAJ