title: Can body mass index predict clinical outcomes for patients with acute lung injury/acute respiratory distress syndrome? A meta-analysis.
abstract: BACKGROUND
  The effects of body mass index (BMI) on the prognosis of acute respiratory distress syndrome (ARDS) are controversial. We aimed to further determine the relationship between BMI and the acute outcomes of patients with ARDS.
  
  
  METHODS
  We searched the Pubmed, Embase, Medline, Cochrane Central Register of Controlled Trials (CENTRAL), and ISI Web of Science for trials published between 1946 and July 2016, using "BMI" or "body mass index" or "overweight" or "obese" and "ARDS" or "ALI" or "acute respiratory distress syndrome" or "acute lung injury", without limitations on publication type or language. Heterogeneity and sensitivity analyses were conducted, and a random-effects model was applied to calculate the odds ratio (OR) or mean difference (MD). Review Manager (RevMan) was used to test the hypothesis using the Mann-Whitney U test. The primary outcome was unadjusted mortality, and secondary outcomes included mechanical ventilation (MV)-free days and length of stay (LOS) in the intensive care unit (ICU) and in hospital.
  
  
  RESULTS
  Five trials with a total of 6268 patients were pooled in our final analysis. There was statistical heterogeneity between normal-weight and overweight patients in LOS in the ICU (I2= 71%, χ2= 10.27, P = 0.02) and in MV-free days (I2= 89%, χ2= 18.45, P < 0.0001). Compared with normal weight, being underweight was associated with higher mortality (OR 1.59, 95% confidence interval (CI) 1.22, 2.08, P = 0.0006), while obesity and morbid obesity were more likely to result in lower mortality (OR 0.68, 95% CI 0.57, 0.80, P < 0.00001; OR 0.72, 95% CI 0.56, 0.93, P = 0.01). MV-free days were much longer in patients with morbid obesity (MD 2.64, 95% CI 0.60, 4.67, P = 0.01), but ICU and hospital LOS were not influenced by BMI. An important limitation of our analysis is the lack of adjustment for age, sex, illness severity, comorbid illness, and interaction of outcome parameters.
  
  
  CONCLUSIONS
  Obesity and morbid obesity are associated with lower mortality in patients with ARDS.
authors.affiliation: Departments of Respiratory Diseases, West China School of Medicine and West China Hospital, Sichuan University, No. 37 Guoxue Alley, Chengdu, 610041, Sichuan, China.
authors.forename: Yue-Nan
authors.initials: YN
authors.lastname: Ni
authors.affiliation: Departments of Respiratory Diseases, West China School of Medicine and West China Hospital, Sichuan University, No. 37 Guoxue Alley, Chengdu, 610041, Sichuan, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Luo
authors.affiliation: Departments of Critical Care Medicine, West China School of Medicine and West China Hospital, Sichuan University, 37 Gue Xue Xiang, Chengdu, 610041, Sichuan, China.
authors.forename: He
authors.initials: H
authors.lastname: Yu
authors.affiliation: Departments of Respiratory Diseases, West China School of Medicine and West China Hospital, Sichuan University, No. 37 Guoxue Alley, Chengdu, 610041, Sichuan, China.
authors.forename: Yi-Wei
authors.initials: YW
authors.lastname: Wang
authors.affiliation: Departments of Respiratory Diseases, West China School of Medicine and West China Hospital, Sichuan University, No. 37 Guoxue Alley, Chengdu, 610041, Sichuan, China.
authors.forename: Yue-Hong
authors.initials: YH
authors.lastname: Hu
authors.affiliation: Departments of Critical Care Medicine, West China School of Medicine and West China Hospital, Sichuan University, 37 Gue Xue Xiang, Chengdu, 610041, Sichuan, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Liu
authors.affiliation: Departments of Respiratory Diseases, West China School of Medicine and West China Hospital, Sichuan University, No. 37 Guoxue Alley, Chengdu, 610041, Sichuan, China. liangbinmiao@163.com.
authors.forename: Bin-Miao
authors.initials: BM
authors.lastname: Liang
authors.affiliation: Departments of Respiratory Diseases, West China School of Medicine and West China Hospital, Sichuan University, No. 37 Guoxue Alley, Chengdu, 610041, Sichuan, China. niyuenantg@126.com.
authors.forename: Zong-An
authors.initials: ZA
authors.lastname: Liang
mesh_terms: D055371:Acute Lung Injury / Q000150:complications* / Q000401:mortality; D015992:Body Mass Index; D006801:Humans; D007362:Intensive Care Units / Q000458:organization & administration / Q000706:statistics & numerical data; D007902:Length of Stay / Q000639:trends; D009765:Obesity / Q000150:complications / Q000401:mortality; D050177:Overweight / Q000150:complications / Q000401:mortality; D063868:Patient Outcome Assessment; D011379:Prognosis; D012128:Respiratory Distress Syndrome / Q000150:complications* / Q000401:mortality; D018709:Statistics, Nonparametric
keywords: Adult; Body mass index; Mortality; Obese; Prognosis; Respiratory distress syndrome