Schnohr et al. 2015, Dose of jogging and mortality

Copenhagen City Heart Study (1,098 joggers, 3,950 non-joggers). Reported a reverse J-shaped curve, with light and moderate joggers having lowest mortality and strenuous joggers no benefit over sedentary people. The high-dose groups were tiny: the >4 h/week category held only 47 joggers with 1 death, so the headline ‘too much running’ finding rests on almost no events and is statistically fragile. Observational. Weak basis for the harm claim.