Infections Are Associated With Increased Risk of Giant Cell Arteritis: A Population-based Case-control Study from Southern Sweden

Objective. To investigate the association between infections and the subsequent development of giant cell arteritis (GCA) in a large population-based cohort from a defined geographic area in Sweden. Methods. Patients diagnosed with biopsy-confirmed GCA between 2000 and 2016 were identified through the database of the Department of Pathology in SkIne, the southernmost region of Sweden. For each GCA case, 10 controls matched for age, sex, and area of residence were randomly selected from the general population. Using the Skine Healthcare Register, we identified all infection events prior to patients' date of GCA diagnosis and controls' index date. With infection as exposure, a conditional logistic regression model was employed to estimate the OR for developing GCA. The types of infections contracted nearest in time to the GCA diagnosis/index date were identified. Results. A total of 1005 patients with biopsy-confirmed GCA (71% female) and 10,050 controls were included in the analysis. Infections were more common among patients subsequently diagnosed with GCA compared to controls (51% vs 41%, OR 1.78, 95% CI 1.53-2.07). Acute upper respiratory tract infection (OR 1.77, 95% CI 1.47-2.14), influenza and pneumonia (OR 1.72, 95 % CI 1.35-2.19), and unspecified infections (OR 5.35, 95 % CI 3.46-8.28) were associated with GCA. Neither skin nor gastrointestinal infections showed a correlation. Conclusion. Infections, especially those of the respiratory tract, were associated with subsequent development of biopsy-confirmed GCA. Our findings support the hypothesis that a range of infections may trigger GCA.