title: Paradoxical association between body mass index and in-hospital mortality in elderly patients with chronic obstructive pulmonary disease in Japan.
abstract: OBJECTIVE
  The prevalence and mortality of chronic obstructive pulmonary disease (COPD) in elderly patients are increasing worldwide. Low body mass index (BMI) is a well-known prognostic factor for COPD. However, the obesity paradox in elderly patients with COPD has not been well elucidated. We investigated the association between BMI and in-hospital mortality in elderly COPD patients.
  
  
  METHODS
  Using the Diagnosis Procedure Combination database in Japan, we retrospectively collected data for elderly patients (>65 years) with COPD who were hospitalized between July 2010 and March 2013. We performed multivariable logistic regression analysis to compare all-cause in-hospital mortality between patients with BMI of <18.5 kg/m2 (underweight), 18.5-22.9 kg/m2 (low-normal weight), 23.0-24.9 kg/m2 (high-normal weight), 25.0-29.9 kg/m2 (overweight), and ≥30.0 kg/m2 (obesity) with adjustment for patient backgrounds.
  
  
  RESULTS
  In all, 263,940 eligible patients were identified. In-hospital mortality was 14.3%, 7.3%, 4.9%, 4.3%, and 4.4%, respectively, in underweight, low-normal weight, high-normal weight, overweight, and obese patients. Underweight patients had a significantly higher mortality than low-normal weight patients (odds ratio [OR]: 1.55, 95% confidence interval [CI]: 1.48-1.63), whereas lower mortality was associated with high-normal weight (OR: 0.76, CI: 0.70-0.82), overweight (OR: 0.73, CI: 0.66-0.80), and obesity (OR: 0.67, CI: 0.52-0.86). Higher mortality was significantly associated with older age, male sex, more severe dyspnea, lower level of consciousness, and lower activities of daily living.
  
  
  CONCLUSIONS
  Overweight and obese patients had a lower mortality than low-normal weight patients, which supports the obesity paradox.
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan ; Division for Health Service Promotion, The University of Tokyo, Tokyo, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Yamauchi
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Wakae
authors.initials: W
authors.lastname: Hasegawa
authors.affiliation: Department of Clinical Epidemiology and Health Economics, School of Public Health, The University of Tokyo, Tokyo, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Yasunaga
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Sunohara
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan ; Division for Health Service Promotion, The University of Tokyo, Tokyo, Japan.
authors.forename: Taisuke
authors.initials: T
authors.lastname: Jo
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Takami
authors.affiliation: Department of Clinical Epidemiology and Health Economics, School of Public Health, The University of Tokyo, Tokyo, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Matsui
authors.affiliation: Department of Health Policy and Informatics, Tokyo Medical and Dental University, Graduate School of Medicine, Tokyo, Japan.
authors.forename: Kiyohide
authors.initials: K
authors.lastname: Fushimi
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Takahide
authors.initials: T
authors.lastname: Nagase
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D016009:Chi-Square Distribution; D015897:Comorbidity; D016208:Databases, Factual; D005260:Female; D017052:Hospital Mortality; D006760:Hospitalization; D006801:Humans; D007564:Japan / Q000453:epidemiology; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D009765:Obesity / Q000175:diagnosis / Q000401:mortality*; D016017:Odds Ratio; D065840:Protective Factors; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000401:mortality*; D012189:Retrospective Studies; D012307:Risk Factors; D013851:Thinness / Q000175:diagnosis / Q000401:mortality*; D013997:Time Factors
keywords: COPD; mortality; obesity paradox