title: Effect of body mass index on mortality and clinical status in rheumatoid arthritis.
abstract: OBJECTIVE
  To study the relative risk (RR) of all-cause and cause-specific mortality in rheumatoid arthritis (RA) associated with body mass index (BMI), and to quantify the clinical and outcome consequences of abnormal BMI.
  
  
  METHODS
  We studied mortality in 24,535 patients over 12.3 years, dividing patients into 3 age groups, <50, 50-70, and >70 years and fit Cox regression models separately within each age stratum. We used BMI categories of <18.5 kg/m(2) (underweight), 18.5 to <25 kg/m(2) (normal weight, reference category), 25 to <30 kg/m(2) (overweight), and ≥30 kg/m(2) (obesity).
  
  
  RESULTS
  BMI ≥30 kg/m(2) was seen in 63-68% and underweight in ~2%. Reduction in the RR (95% confidence interval [95% CI]) for all-cause (AC) and cardiovascular mortality was seen for overweight (AC 0.8 [95% CI 0.8, 0.9]) and obese groups (AC 0.8 [95% CI 0.7, 0.8]), with and without comorbidity adjustment. Underweight was associated with increased mortality risk (AC 1.9 [95% CI 1.7, 2.3]). By contrast, obesity produced profound changes in clinical variables. Compared with normal weight, the odds ratio in the obese group was 4.8 for diabetes mellitus, 3.4 for hypertension, 1.3 for myocardial infarction, 1.4 for joint replacement, and 1.9 for work disability. Total semiannual direct medical costs were $1,683 greater, annual household income $6,481 less, pain scores 1.1 units higher, Health Assessment Questionnaire 0.28 higher, and EuroQol utility 0.7 units lower in the obese.
  
  
  CONCLUSIONS
  Overweight and obesity reduce the RR of all-cause and cardiovascular mortality across different age groups and durations of RA. By contrast, overweight and obesity are associated with substantial increased risks of comorbidity, total joint replacement, greater pain, medical costs, and decreased quality of life.
authors.affiliation: National Data Bank for Rheumatic Diseases and University of Kansas School of Medicine, Wichita, KS 67214, USA. fwolfe@arthritis-research.org
authors.forename: Frederick
authors.initials: F
authors.lastname: Wolfe
authors.forename: Kaleb
authors.initials: K
authors.lastname: Michaud
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000150:complications / Q000401:mortality* / Q000503:physiopathology; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D050177:Overweight / Q000150:complications / Q000401:mortality* / Q000503:physiopathology; D012306:Risk