Methods matter: population attributable fraction (PAF) in sport and exercise medicine

Physical inactivity kills as many people as smoking —a newspaper heading reads1 following a Lancet publication2 suggesting that more than 5 million deaths would be avoided annually if all inactive people exercised. The statistic that provided this data point (5 million deaths) is called the population attributable fraction (PAF).3 PAF is an estimate of the health impact of an exposure (eg, physical inactivity, high-carbohydrate diet) on a health...