title: Obesity is a risk factor for peritonitis in the Australian and New Zealand peritoneal dialysis patient populations.
abstract: OBJECTIVE
  The aim of the present investigation was to examine the association between body mass index (BMI) and peritonitis rates among incident peritoneal dialysis (PD) patients in a large cohort with long-term follow-up.
  
  
  METHODS
  Retrospective observational cohort study of the Australian and New Zealand PD patient population.
  
  
  METHODS
  Australia and New Zealand Dialysis and Transplant (ANZDATA) Registry.
  
  
  METHODS
  The study included all incident adult patients (n = 10 709) who received PD in Australia and New Zealand in the 12-year period between 1 April 1991 and 31 March 2003. Patients were classified as obese (BMI > or = 30 kg/m2), overweight (BMI 25.0 - 29.9 kg/m2), normal weight (20 - 24.9 kg/m2), or underweight (< 20 kg/m2).
  
  
  METHODS
  Time to first peritonitis and episodes of peritonitis per patient-year were recorded over the 12-year period.
  
  
  RESULTS
  Higher BMI was associated with a shorter time to first peritonitis episode, independent of other risk factors [hazard ratio 1.08 for each 5-kg/m2 increase in BMI, 95% confidence interval (CI) 1.04 - 1.12, p < 0.001]. When peritonitis outcomes were analyzed as episodes of peritonitis per patient-year, these rates were significantly higher among patients with higher BMI: underweight 0.69 episodes/year (95% CI 0.66 - 0.73), normal weight 0.79 (95% CI 0.77 - 0.81), overweight 0.88 (95% CI 0.85 - 0.90), obese 1.06 (95% CI 1.02 - 1.09). Coronary artery disease and chronic lung disease were associated with both shorter time to first peritonitis and higher peritonitis rates, independently of these other factors. There was also a "vintage effect," with lower peritonitis rates seen among people who commenced dialysis in more recent years.
  
  
  CONCLUSIONS
  Higher BMI at the commencement of renal replacement therapy is a significant risk factor for peritonitis. The mechanisms for this remain undefined.
authors.affiliation: ANZDATA Registry, Adelaide, South Australia. stephenm@anzdata.org.au
authors.forename: Stephen P
authors.initials: SP
authors.lastname: McDonald
authors.forename: John F
authors.initials: JF
authors.lastname: Collins
authors.forename: Markus
authors.initials: M
authors.lastname: Rumpsfeld
authors.forename: David W
authors.initials: DW
authors.lastname: Johnson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001315:Australia / Q000453:epidemiology; D015992:Body Mass Index; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007676:Kidney Failure, Chronic / Q000150:complications / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D009765:Obesity / Q000150:complications / Q000453:epidemiology*; D010530:Peritoneal Dialysis; D010538:Peritonitis / Q000453:epidemiology* / Q000209:etiology*; D012042:Registries; D012189:Retrospective Studies; D012307:Risk Factors