title: Incidence of total knee and hip replacement for osteoarthritis in relation to the metabolic syndrome and its components: a prospective cohort study.
abstract: OBJECTIVE
  To examine whether components of metabolic syndrome (MetS), either singly or additively, were associated with the incidence of severe knee and hip OA, and whether these associations were independent of obesity assessed by body mass index (BMI).
  
  
  METHODS
  Twenty thousand, four hundred and thirty participants who had blood lipids, anthropometric and blood pressure measurements during 2003-2007 were selected from the Melbourne Collaborative Cohort Study. MetS was defined as central obesity assessed by waist circumference and any two of raised triglyceride level, reduced HDL cholesterol level, hypertension or impaired fasting glycaemia. The incidence of total knee and hip replacement was determined by linking cohort records to the Australian Orthopaedic Association National Joint Replacement Registry.
  
  
  RESULTS
  Six hundred and sixty participants had knee OA and 562 had hip OA. After adjustment for age, gender, country of birth, education, physical activity and BMI, central obesity [hazard ratio (HR) 1.59, 95% confidence interval (CI) 1.25-2.01] and hypertension (1.24, 1.05-1.48) were associated with increased risk of knee OA. The accumulation of MetS components was associated with knee OA risk, independent of BMI: one component, 2.12 (1.15-3.91); two components, 2.92 (1.60-5.33) and three or more components, 3.09 (1.68-5.69). No statistically significant associations were observed for hip OA.
  
  
  CONCLUSIONS
  Cumulative number of MetS components and central obesity and hypertension were associated with increased risk of severe knee OA, independent of BMI. No associations were observed with severe hip OA. These findings suggest that the pathogenesis of knee and hip OA differ and that targeting the management of MetS may reduce the risk of knee OA.
authors.affiliation: Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, Victoria 3004, Australia.
authors.forename: Sultana
authors.initials: S
authors.lastname: Monira Hussain
authors.affiliation: Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, Victoria 3004, Australia.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, Victoria 3004, Australia.
authors.forename: Flavia M
authors.initials: FM
authors.lastname: Cicuttini
authors.affiliation: Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, Melbourne School of Population and Global Health, University of Melbourne, Carlton, Victoria, Australia; Cancer Epidemiology Centre, Cancer Council Victoria, Carlton, Victoria, Australia.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Simpson
authors.affiliation: Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, Victoria 3004, Australia; Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, Melbourne School of Population and Global Health, University of Melbourne, Carlton, Victoria, Australia; Cancer Epidemiology Centre, Cancer Council Victoria, Carlton, Victoria, Australia.
authors.forename: Graham G
authors.initials: GG
authors.lastname: Giles
authors.affiliation: Department of Orthopaedic, Repatriation General Hospital, Daw Park, South Australia, Australia; Australian Orthopaedic Association National Joint Replacement Registry, Discipline of Public Health, School of Population Health & Clinical Practice, University of Adelaide, South Australia, Australia.
authors.forename: Stephen
authors.initials: S
authors.lastname: Graves
authors.affiliation: Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, Victoria 3004, Australia. Electronic address: anita.wluka@monash.edu.
authors.forename: Anita E
authors.initials: AE
authors.lastname: Wluka
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000706:statistics & numerical data*; D019645:Arthroplasty, Replacement, Knee / Q000706:statistics & numerical data*; D015992:Body Mass Index; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D024821:Metabolic Syndrome / Q000150:complications*; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000150:complications / Q000601:surgery*; D020370:Osteoarthritis, Knee / Q000150:complications / Q000601:surgery*; D011446:Prospective Studies; D012307:Risk Factors; D055105:Waist Circumference
keywords: Osteoarthritis; The metabolic syndrome; Total hip replacement; Total knee replacement