title: The Dose-Response Relationship Between Body Mass Index and Mortality in Subjects Admitted to the ICU With and Without Mechanical Ventilation.
abstract: BACKGROUND
  Obesity has been associated with increased mortality in the general population, whereas a paradoxical relationship between higher body mass index and lower mortality has been referred to as the obesity paradox in critically ill patients. However, it remains unknown whether a particular subgroup is most affected. The aim of the present study is to elucidate whether obesity is associated with lower mortality in the ICU population by comparing subjects with and without mechanical ventilation.
  
  
  METHODS
  A total of 334,238 subjects from a nationwide database who were discharged between July 2010 and March 2012 and who were admitted to general ICUs during their hospitalization were included in this study. The primary outcome was in-hospital mortality.
  
  
  RESULTS
  Of all subjects evaluated, 23.3% were started on mechanical ventilation within the first 2 d after ICU admission. Compared with the non-ventilated group, the ventilated group was more likely to have sepsis, pneumonia, or coma. The ventilated group underwent more procedures within the first 2 d after ICU admission compared with the non-ventilated group. A restricted cubic spline function showed lower mortality in subjects with a higher body mass index among the ventilated group, whereas mortality was increased with increasing body mass index in the non-ventilated group.
  
  
  CONCLUSIONS
  This study shows that a high body mass index is associated with low mortality in the mechanically ventilated group, whereas the non-ventilated group showed a reverse J-shaped association. There was a higher mortality rate in underweight subjects in both groups.
authors.affiliation: Department of Clinical Epidemiology and Health Economics, School of Public Health, University of Tokyo, Tokyo yasunagah-tky@umin.ac.jp sasabuchi-tky@umin.ac.jp.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Sasabuchi
authors.affiliation: Department of Clinical Epidemiology and Health Economics, School of Public Health, University of Tokyo, Tokyo yasunagah-tky@umin.ac.jp sasabuchi-tky@umin.ac.jp.
authors.forename: Hideo
authors.initials: H
authors.lastname: Yasunaga
authors.affiliation: Department of Clinical Epidemiology and Health Economics, School of Public Health, University of Tokyo, Tokyo.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Matsui
authors.affiliation: Department of Surgery, Jichi Medical University, Tochigi.
authors.forename: Alan T
authors.initials: AT
authors.lastname: Lefor
authors.affiliation: Department of Clinical Data Management and Research, Clinical Research Center, National Hospital Organization Headquarters, Tokyo.
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Horiguchi
authors.affiliation: Department of Health Policy and Informatics, Tokyo Medical and Dental University Graduate School of Medicine, Tokyo.
authors.forename: Kiyohide
authors.initials: K
authors.lastname: Fushimi
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Jichi Medical University Saitama Medical Center, Saitama, Japan.
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Sanui
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D016208:Databases, Factual; D005260:Female; D017052:Hospital Mortality; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D007564:Japan; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000401:mortality; D012121:Respiration, Artificial / Q000401:mortality*; D012189:Retrospective Studies; D013851:Thinness / Q000401:mortality
keywords: ICU; body mass index; mechanical ventilation; obesity; obesity paradox; restricted cubic spline