title: BMI upon discharge from hospital and its relationship with survival: an observational study utilising linked patient records.
abstract: OBJECTIVE
  Current advice for patients being discharged from hospital suggests a body mass index of 18.5 to 24 kgm-2, although this aspirational target may often not be achieved. We examined the relationship between body mass index on discharge from hospital and subsequent mortality over a maximum follow-up of 3.8 years.
  
  
  METHODS
  We conducted a survival analysis using linked hospital records data with national hospital episode statistics and national death certification data.
  
  
  METHODS
  The analysis included adult patients who were admitted to University Hospitals Birmingham NHS Foundation Trust for a period of over 24 h during 2011, excluding day cases and regular day case attenders.
  
  
  METHODS
  The relationship between body mass index and mortality at medium term was estimated separately in both men and women, after accounting for case-mix.
  
  
  RESULTS
  For both males and females, the relationship between body mass index at discharge and the loge hazard of death was strongly non-linear (p = 0.0002 for females and p < 0.0001 for males) and predictive (both p < 0.0001). In all models, the optimal body mass index range associated with best survival was 25 to 35 kgm-2, with a sharp increase in risk for lower body mass index.
  
  
  CONCLUSIONS
  There was little evidence to support current aspirational body mass index targets in the discharge population. Hospitals should ensure adequate nutrition especially among those with a reduced body mass index.
authors.affiliation: 1 Department of Primary Care and Population Health, University College London, London WC1E 6BT, UK.|2 Quality and Outcomes Research Unit, University Hospital Birmingham NHS Foundation Trust, Birmingham B15 2PR, UK.
authors.forename: Nick
authors.initials: N
authors.lastname: Freemantle
authors.affiliation: 3 FARR Institute of Health Informatics, University College London, London WC1E 6BT, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: Ray
authors.affiliation: 1 Department of Primary Care and Population Health, University College London, London WC1E 6BT, UK.
authors.forename: Milena
authors.initials: M
authors.lastname: Falcaro
authors.affiliation: 2 Quality and Outcomes Research Unit, University Hospital Birmingham NHS Foundation Trust, Birmingham B15 2PR, UK.
authors.forename: David
authors.initials: D
authors.lastname: McNulty
authors.affiliation: 3 FARR Institute of Health Informatics, University College London, London WC1E 6BT, UK.
authors.forename: Laura
authors.initials: L
authors.lastname: Shallcross
authors.affiliation: 1 Department of Primary Care and Population Health, University College London, London WC1E 6BT, UK.
authors.forename: John
authors.initials: J
authors.lastname: Wood
authors.affiliation: 2 Quality and Outcomes Research Unit, University Hospital Birmingham NHS Foundation Trust, Birmingham B15 2PR, UK.|4 School of Clinic and Experimental Medicine, University of Birmingham, West Midlands B15 2TT, UK.
authors.forename: Domenico
authors.initials: D
authors.lastname: Pagano
keywords: Evidence-based practice; metabolism; nutrition