title: A United Kingdom perspective on the relationship between body mass index (BMI) and bone health: a cross sectional analysis of data from the Nottingham Fracture Liaison Service.
abstract: OBJECTIVE
  This study examines the relationship between high BMI, a diagnosis of osteoporosis and low trauma fractures.
  
  
  METHODS
  This is a cross sectional analysis using data collected from the Nottingham Fracture Liaison Service. A total of 4288 participants with a low trauma fracture from 1 January 2007 to 31 August 2012 were analysed. Logistic regression adjusted for potential confounders was used investigate osteoporosis and BMI. Fracture types were compared between those who were obese and non-obese.
  
  
  RESULTS
  A total of 30% (1285) were obese. Prevalence of osteoporosis was 13.4%, 24.9%, and 40.4% in the obese, overweight and normal category respectively. Being obese has an odds ratio of 0.23 (95% CI 0.19-0.28, p<0.01) of having osteoporosis compared to a normal BMI category. When variable BMI cut offs were used (BMI 25, 30 and 35) to calculate the positive predictive value of patients not having osteoporosis, it was 80.5%, 86.3% and 88.3%. Examining fracture types, obese patients when compared with the non-obese category, were more likely to fracture their ankle (OR 1.48, p<0.01) and upper arm (OR 1.48, p<0.001), but were less likely to fracture their wrist (OR 0.65, p<0.001). In the elderly (>70years), obesity no longer influenced ankle or wrist fractures but there is an increased risk of upper arm fractures (OR 1.46, p=0.005).
  
  
  CONCLUSIONS
  Higher BMD in obesity is not protective against fractures as there are a significant number of fractures in this group which may be due to body habitus, mechanism of injury and the effect of adiposity on bone. A low trauma osteoporotic fracture will need to be redefined in light of these findings.
authors.affiliation: Department of Healthcare for Older People, Queens Medical Centre, Nottingham NG7 2UH, UK. Electronic address: terenceong@doctors.org.uk.
authors.forename: Terence
authors.initials: T
authors.lastname: Ong
authors.affiliation: Department of Healthcare for Older People, Queens Medical Centre, Nottingham NG7 2UH, UK.
authors.forename: Opinder
authors.initials: O
authors.lastname: Sahota
authors.affiliation: Nottingham Clinical Trials Unit, University of Nottingham, Queens Medical Centre, Nottingham NG7 2UH, UK.
authors.forename: Wei
authors.initials: W
authors.lastname: Tan
authors.affiliation: Department of Trauma and Orthopaedics, Queens Medical Centre, Nottingham NG7 2UH, UK.
authors.forename: Lindsey
authors.initials: L
authors.lastname: Marshall
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D015992:Body Mass Index; D015519:Bone Density; D001842:Bone and Bones / Q000473:pathology*; D003430:Cross-Sectional Studies; D005260:Female; D050723:Fractures, Bone / Q000150:complications / Q000000981:diagnostic imaging / Q000453:epidemiology*; D006801:Humans; D008297:Male; D009765:Obesity / Q000150:complications; D016017:Odds Ratio; D010024:Osteoporosis / Q000150:complications / Q000000981:diagnostic imaging / Q000453:epidemiology; D006113:United Kingdom / Q000453:epidemiology
keywords: Body mass index; Bone density; Bone fractures; Bone fragility; Obesity; Osteoporosis