Association between body mass index and anti-citrullinated protein antibody-positive and anti-citrullinated protein antibody-negative rheumatoid arthritis: results from a population-based case-control study.
OBJECTIVE
Being overweight or obese is associated with many chronic diseases, but previous studies of the association with rheumatoid arthritis (RA) have shown inconsistent results. The aim of this study was to investigate the association between body mass index (BMI) and the risk of developing the 2 main subtypes of RA.


METHODS
At inclusion, cases and controls answered questions about their weight and height and donated blood samples. The presence of antibodies to citrullinated protein antigens (ACPAs) was analyzed among 2,748 cases and 3,444 controls (28% men). Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated using conditional logistic regression.


RESULTS
Compared to those with normal weight (BMI <25 kg/m(2) ), the adjusted overall OR for developing ACPA-negative RA was 1.1 (95% CI 0.9-1.3) for overweight individuals (BMI ≥25 to <30 kg/m(2) ) and 1.4 (95% CI 1.1-1.9) for obese individuals (BMI ≥30 kg/m(2) ). When stratified by sex, the OR for ACPA-negative RA for obese women was 1.6 (95% CI 1.2-2.2), and there was no association between obesity and ACPA-negative RA in men (OR 1.1, 95% CI 0.6-1.8). In obese men compared to men with normal weight, the OR for ACPA-positive RA was 0.6 (95% CI 0.3-0.9), while there was no association between BMI and ACPA-positive RA among women (OR 1.0, 95% CI 0.8-1.2).


CONCLUSIONS
Our findings show that obesity is associated with developing ACPA-negative RA in women, and indicate an inverse association between BMI and ACPA-positive RA in men.
Karolinska Institute, Stockholm, Sweden. annmarie.wesley@ki.se
Annmarie
A
Wesley
Camilla
C
Bengtsson
Ann-Charlotte
AC
Elkan
Lars
L
Klareskog
Lars
L
Alfredsson
Sara
S
Wedrén
D001172:Arthritis, Rheumatoid / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology; D001323:Autoantibodies / Q000097:blood*; D015992:Body Mass Index; D016022:Case-Control Studies; D015897:Comorbidity; D005260:Female; D006801:Humans; D008297:Male; D016555:Matched-Pair Analysis; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000453:epidemiology* / Q000276:immunology; D010456:Peptides, Cyclic / Q000097:blood*; D012016:Reference Values; D012307:Risk Factors; D016036:Seroepidemiologic Studies; D012737:Sex Factors; D013548:Sweden / Q000453:epidemiology
D001323:Autoantibodies; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide