Body mass index and the risk of giant cell arteritis: results from a prospective study.

OBJECTIVE The aim of this study was to examine potential risk factors for GCA in a nested case-control study based on two prospective health surveys. METHODS We used two population-based health surveys, the Malmö Preventive Medicine Program (MPMP) and the Malmö Diet Cancer Study (MDCS). Individuals who developed GCA after inclusion were identified by linking the MPMP and MDCS databases to several patient administrative registers. A structured review of the medical records of all identified cases was performed. Four controls for every confirmed case, matched for sex, year of birth and year of screening, were selected from the corresponding databases. Potential predictors of GCA were examined in conditional logistic regression models. RESULTS Eighty-three patients (70% women, 64% biopsy positive, mean age at diagnosis 71 years) had a confirmed diagnosis of GCA after inclusion in the MPMP or MDCS. A higher BMI was associated with a significantly reduced risk of subsequent development of GCA [odds ratio (OR) 0.91/kg/m(2) (95% CI 0.84, 0.98)]. Smoking was not a risk factor for GCA overall [OR 1.36 (95% CI 0.77, 2.57)], although there was a trend towards an increased risk in female smokers [OR 2.14 (95% CI 0.97, 4.68)]. In multivariate analysis, adjusted for smoking and level of formal education, the inverse association between BMI and GCA remained significant (P = 0.027). CONCLUSION In this study, GCA was predicted by a lower BMI at baseline. Potential explanations include an effect of reduced adipose tissue on hormonal pathways regulating inflammation.