Background/Purpose: Giant cell arteritis (GCA) is a vasculitis that affects large and medium sized arteries in people 50 years or older. Gout, the most common inflammatory arthritis in adults, is characterized by the activation of inflammasome and an increased production of pro-inflammatory cytokines, such as IL-1 beta (IL-1β), IL-6, IL-18 and others, which also play a central role in GCA. Our objective was to assess whether gout in the elderly is associated with a risk of incident GCA.

Methods: We used the 5% Medicare claims data from 2006-2012 for this cohort study. Gout was identified by the presence of two claims for gout at least 4 weeks apart, with International Classification of Diseases, ninth revision, common modification (ICD-9-CM) code of 274.xx. Study outcome was incident GCA, identified by two claims for GCA with an ICD-9-CM code of 446.5, at least 4 weeks apart and an absence of GCA claims in the baseline 365-day period, a valid approach. We used multivariable-adjusted Cox proportional hazard models to assess the association of gout with incident GCA, adjusting for potential confounders/covariates including demographics (age, race, gender), comorbidities (Charlson-Romano comorbidity index), and medications commonly used for cardiac diseases (statins, beta-blockers, diuretics, and angiotensin converting enzyme (ACE)-inhibitors) and gout (allopurinol and febuxostat; Model 1).  

Results: Among 1,737,027 eligible people in the study cohort, there were 3,004 cases of incident GCA during the follow-up; 2,808 in people without gout and 196 in people with gout. People with gout and incident GCA has a mean duration of gout of 2.2 years prior to the GCA diagnosis (SD, 1.7; median, 1.8; IQR, 0.5, 3.5 years). The crude incidence rate of GCA was 28.0 per 100,000 person-years in people without gout and 63.7 per 100,000 person-years in people with gout. The GCA incidence rate of 28/100,000 in our non-gout population mirrored the incidence rate of 19 to 29/100,000 noted in 50+ year-olds in the three largest population-based studies of GCA. In the main multivariate model, gout was associated with an increased risk of incident GCA, HR was 2.05 (95% CI, 1.82, 2.54; Table 1). Women were 2.2-times more likely to have incident GCA compared to men, older age was associated with a higher risk and having 2 or more comorbidities was associated with a 1.7-times HR of incident GCA. Compared to white, black or other race were each associated with 0.6-0.7 times HR of incident GCA (Table 1).

Conclusion: Gout was independently associated with 2-fold higher risk of GCA in the older individuals after adjustment for demographics, comorbidity and medications, and the risk could be between 1.4 to 1.9-fold higher risk. Future studies need to confirm this finding and evaluate the underlying mechanism of this novel association.