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