Body mass index and mortality in chronic obstructive pulmonary disease A dose-response meta-analysis

The aim of this study is to summarize the evidence on the dose-response relationship between body mass index (BMI) and mortality in patients with chronic obstructive pulmonary disease (COPD). We performed a systemic literature search in PubMed, Embase, and Web of Science for relevant studies that were published until June 2015. A random effects meta-analysis was used to estimate the pooled relative risks (RRs) of all-cause mortality in COPD patients with normal weight compared with those who were underweight, overweight, or obese. In addition, a dose-response meta-analysis was conducted to explore the dose-response relationship between BMI and all-cause mortality in COPD patients. A total of 17 observational studies involving 30,182 COPD patients among 285,960 participants were included. Compared with the reference category, the RRs of underweight, overweight, and obese individuals were 1.40 (95% confidence interval (CI), 1.20-1.63), 0.80 (95% CI, 0.67-0.96), and 0.77 (95% CI, 0.62-0.95), respectively. A significant nonlinear relationship between BMI and mortality of COPD patients was found by using a random effects model. COPD patients with BMI of <21.75kg/m(2) had a higher risk of death. Moreover, an increase in the BMI resulted in a decrease in the risk of death. The risk of death was lowest when BMI was 30kg/m(2) (RR= 0.69; 95% CI, 0.53-0.89). The BMI was not associated with all-cause mortality when BMI was >32kg/m(2). Our findings indicate that overweight is associated with a lower risk of all-cause mortality among patients with COPD whereas underweight is associated with a higher risk of all-cause mortality in these patients. However, there is limited evidence to support the association between obesity and the risk of all-cause mortality in patients with COPD.