Meta-analysis of the relation of body mass index to all-cause and cardiovascular mortality and hospitalization in patients with chronic heart failure

Clinical studies have indicated the existence of an "obesity paradox" in patients with chronic heart failure (HF), that is, reduced mortality in patients who have elevated body mass index (BMI) scores compared with normal-weight reference groups. The aim of this study was to investigate the relation of BMI with all-cause and cardiovascular (CV) mortality and hospitalization in patients with chronic HF though a systematic review and meta-analysis of published research. PubMed, the Cumulative Index to Nursing and Allied Health Literature, Cochrane Central, Scopus, web of science and Embase were searched for studies reporting rates of total mortality, cardiac mortality, and risk for hospitalization in patients with HF in various BMI categories (<20 kg/m(2) [low], 20 to 24.9 kg/m(2) [normal reference], 25 to 29.9 kg/m(2) [overweight], 30 to 34.9 [obese], and ≥35 kg/m(2) [severely obese]). Event rates were compared using a forest plot of relative risk (RR) using a random-effects model assuming interstudy heterogeneity. Two study investigators independently reviewed the 124 reports retrieved and identified 6 for final analyses (n = 22,807). After a mean follow-up period of 2.85 years, the risk for adverse events was highest in patients with low BMIs: total mortality RR 1.27 (95% confidence interval [CI] 1.17 to 1.37), CV mortality RR 1.20 (95% CI 1.01 to 1.43), and hospitalization RR 1.19 (95% CI 1.09 to 1.30). Risk for CV mortality and hospitalization was lowest in overweight patients (RR 0.79, 95% CI 0.70 to 0.90, and RR 0.92, 95% CI 0.86 to 0.97, respectively). Increasing degree of obesity failed to achieve a statistically significant effect on CV mortality (RR 0.82, 95% CI 0.64 to 1.05, and RR 0.71, 95% CI 0.50 to 1.01, for obese and severely obese, respectively) and on hospitalization (RR 0.99, 95% CI 0.92 to 1.07, and RR 1.28, 95% CI 0.88 to 1.87, for obese and severely obese, respectively). In conclusion, risk for total mortality and CV mortality and hospitalization was highest in patients with chronic HF who were underweight as defined by low BMI, whereas risk for CV mortality and hospitalization was lowest in overweight subjects.