Incidence, survival, and diagnostic trends in GCA across seven decades in a North American population-based cohort.

Objectives: To analyze trends in the incidence and use of diagnostic modalities for GCA in a population-based cohort over the past seven decades. To explore survival trends in patients with GCA compared with the general population.

Methods: A population-based cohort of patients diagnosed with GCA was extended with new incident cases from 2010 to 2019. Three time periods were compared: Period One (1950-1979), Period Two (1980-1999), and Period Three (2000-2019). Cases were classified as: Diagnostic Group One, temporal artery biopsy (TAB) positive; Diagnostic Group Two, TAB-negative or not done with positive large-vessel imaging; or Diagnostic Group Three, clinical diagnosis of GCA. Survival was evaluated by comparing Kaplan-Meier estimated mortality rates for cases of GCA against expected mortality rates from Minnesota life tables RESULTS: Age- and sex-adjusted incident rates per 100,000 ≥ 50 years of age (95% CI) were 13.5 (10.1, 16.9) in Period One, 21.0 (17.1, 25.0) in Period Two, and 15.0 (12.4, 17.5) in Period Three. The percent of patients in Diagnostic Group One decreased over the three time periods (89%, 86%, and 72%) while the patients in Diagnostic Group Three increased (11%, 14%, and 17%). Standardized mortality ratios (95% CI) were 1.03 (0.79, 1.32), 1.11 (0.91, 1.34), and 0.82 (0.64, 1.04) across Periods 1-3, respectively.

Conclusions: Incidence of GCA in females in the population declined, resulting in a decreasing overall incidence. More patients have been identified by large-vessel imaging and fewer by positive TABs. No significant difference in survival between patients with GCA and the general population was observed.