title: Body mass index and mortality in chronic obstructive pulmonary disease: a meta-analysis.
abstract: BACKGROUND
  The association between body mass index (BMI) and mortality in patients suffering from chronic obstructive pulmonary disease (COPD) has been a subject of interest for decades. However, the evidence is inadequate to draw robust conclusions because some studies were generally small or with a short follow-up.
  
  
  METHODS
  We carried out a search in MEDLINE, Cochrane Central Register of Controlled Trials, and EMBASE database for relevant studies. Relative risks (RRs) with 95% confidence interval (CI) were calculated to assess the association between BMI and mortality in patients with COPD. In addition, a baseline risk-adjusted analysis was performed to investigate the strength of this association.
  
  
  RESULTS
  22 studies comprising 21,150 participants were included in this analysis. Compared with patients having a normal BMI, underweight individuals were associated with higher mortality (RR = 1.34, 95% CI = 1.01-1.78), whereas overweight (RR = 0.47, 95% CI = 0.33-0.68) and obese (RR = 0.59, 95% CI = 0.38-0.91) patients were associated with lower mortality. We further performed a baseline risk-adjusted analysis and obtained statistically similar results.
  
  
  CONCLUSIONS
  Our study showed that for patients with COPD being overweight or obese had a protective effect against mortality. However, the relationship between BMI and mortality in different classes of obesity needed further clarification in well-designed clinical studies.
authors.affiliation: Department of Respiratory Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Cao
authors.forename: Ran
authors.initials: R
authors.lastname: Wang
authors.forename: Jianmiao
authors.initials: J
authors.lastname: Wang
authors.forename: Hansvin
authors.initials: H
authors.lastname: Bunjhoo
authors.forename: Yongjian
authors.initials: Y
authors.lastname: Xu
authors.forename: Weining
authors.initials: W
authors.lastname: Xiong
mesh_terms: D015992:Body Mass Index; D001835:Body Weight; D006801:Humans; D009765:Obesity / Q000150:complications / Q000401:mortality; D050177:Overweight / Q000150:complications / Q000401:mortality; D011379:Prognosis; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000401:mortality*; D013851:Thinness / Q000150:complications / Q000401:mortality