To the Editor: Dr Sui and colleagues1 studied cardiorespiratory fitness and adiposity as mortality predictors in older adults. I have several questions about this study.
First, other studies have found that physical activity, even with some measurement errors, is associated with cardiovascular fitness with a beneficial association with cardiovascular disease and all-cause mortality.2- 4 However, in this study, the rates of physical inactivity were virtually identical in survivors and decedents (25%). It is not clear why there would be an association of mortality with low fitness but not with physical inactivity.
Wei M. Cardiorespiratory Fitness, Adiposity, and Mortality. JAMA. 2008;299(9):1013-1014. doi:10.1001/jama.299.9.1013-a