The protective effects of a novel fitness‐fatness index on all‐cause mortality among adults with cardiovascular disease

Background We evaluated the specific association between a fitness‐fatness index ( FFI ) and all‐cause mortality among a national sample of US adults with coronary artery disease, congestive heart failure, or myocardial infarction. This FFI has recently emerged in the literature as a novel index of health. Hypothesis We hypothesize that FFI will be inversely associated with mortality risk. Methods The FFI was calculated as cardiorespiratory fitness divided by waist‐to‐height ratio. Data from the 1999–2006 National Health and Nutrition Examination Survey were used to identify 1206 participants, ages 20 to 85. Person‐months of follow‐up were calculated from the date of interview until date of death or censoring on December 31, 2011, whichever came first. Results In a Cox proportional hazards model, for every 1‐ FFI ‐unit increase, participants had a 6% reduced all‐cause mortality rate (hazard ratio [ HR ]: 0.94, 95% confidence interval [ CI ]: 0.91‐0.97, P = 0.001; N = 1206). Results were similar among those diagnosed with coronary artery disease ( HR : 0.94, 95% CI : 0.90‐0.98, P = 0.007), congestive heart failure ( HR : 0.95, 95% CI : 0.91‐0.99, P = 0.02), or myocardial infarction ( HR : 0.96, 95% CI : 0.92‐0.99, P = 0.04). When examined in isolation, only fitness (and not fatness) was linked with survival benefits. Conclusions In this national sample, increased FFI was associated with reduced risk of all‐cause mortality; this association was driven by the beneficial effects of fitness. This underscores the importance of tailored cardiac rehabilitation programs designed to promote fitness, in particular, among cardiac populations.