Incidence of giant cell arteritis and characteristics of patients: data-driven analysis of comorbidities.

Objective: To establish the incidence of giant cell arteritis (GCA), cumulative use of prednisolone, and comorbidities most associated with GCA.

Methods: The data source was the UK Clinical Practice Research Datalink. Selection criteria included ≥1 record of a diagnostic term for GCA between January 1, 2000 and December 31, 2011, age ≥50 years, and ≥1 prescription of oral or systemic corticosteroid. Controls were selected randomly (2:1), with year of birth, practice, and followup duration (<2 or ≥2 years) as matching variables. Analysis was data driven; all comorbidities were identified in a 2-year window, with relative risk (RR) calculated and rank ordered.

Results: A total of 4,671 patients fulfilled the definition of GCA (incidence, 1.0 per 10,000 person-years), with highest incidence (7.4 per 10,000 person-years) in women ages 70-79 years. Of the 4,671 patients, 4,655 (99.7%) were prescribed prednisolone. In the group with ≥2 years' followup (n = 3,074), the mean number of prednisolone prescriptions was 32.1, and the mean cumulative dose was 8,640 mg; 1,034 patients (33.4%) received a cumulative dose of ≥10,000 mg. Comorbidities strongly associated with GCA were polymyalgia rheumatica (RR 14.9, 95% confidence interval [95% CI] 11.9-18.7), visual disturbances (RR 4.6, 95% CI 2.7-7.8), facial pain (RR 3.3, 95% CI 2.1-5.3), osteoporosis (RR 2.9, 95% 2.3-3.7), hypokalemia (RR 2.5, 95% CI 1.6-3.9), and various infections such as oral/esophageal thrush (RR 3.7, 95% CI 2.2-6.0) and herpes zoster (RR 2.6, 95% CI 1.6-4.1).

Conclusion: GCA is relatively uncommon; its incidence peaks at age 70-79 years in women. Overall, GCA patients in the UK are treated with high cumulative prednisolone doses. Many conditions are associated with GCA, including several related to corticosteroid use.