[Effect of physical activity on longevity]

Multiple population studies have reported a positive correlation between higher levels of physical activity (PA) and longer lifespan. It has been generally accepted that it occurs due to PA having a direct effect on longevity. However, this idea is negated by experiments on animal models and an observational study on a twin cohort published recently by Karvinen et al. This unique study includes a pairwise comparison of monozygotic twins discordant for PA, therefore eliminating any influence of genetic factors on both mortality and tendency to take up exercise. The intriguing lack of differences in lifespan in such pairs implies that PA is not an important life prolonging factor. This discovery casts doubt on the validity of PA recommendations found in numerous medical guidelines. Nevertheless, the mentioned results apply only to the plain PA - longevity relation. They do not consider health benefits of PA, for which solid evidence exists. In particular, PA clearly reduces the risk of obesity-related diseases. This may indirectly yet significantly affect the length and quality of life, even if the direct relationship between PA and lifespan will be proven false in further research.