Epidemiology and Genetics

Abstract

Giant cell arteritis (GCA) is the most frequent primary systemic vasculitis among patients ≥50 years of age, peaking in the seventh and eighth decade of life. The annual incidence rate of GCA increases with advancing age up to a maximum in the 70–79 year age group and then decreases slowly. Women are more affected than males with 3:1 ratio. The highest incidence is reported in North European countries and in North American population of the same descent with an incidence that varies between 32.4/100,000 people, older than 50 years of age in Norway and 18.9/100,000 people in Olsted County, Minnesota, USA Prevalence in GCA follows the same latitude distribution of incidence with higher prevalence in the Northern hemisphere compared to the Southern Europe and non-European country. Prevalence study from Mayo Clinic reported that prevalence rate of GCA between 1950 and 2009 among women was 304 (95% CI 229–375) and among men was 91 (95% CI 46–156) per 100,000 population older than 50 years of age. Compared with general population, all cause SMR (standardized mortality ratio) was not increased in GCA patients (SMR 1.081, 95% CI 0.963–1.214, p = 0.184) and the stratification by regions showed no significant increase in all cause SMR in Europe and the USA. Sex-specific meta-analysis provided by four out of eight studies included revealed the pooled SMR for women was 1.046 (95% CI 0.834–1.314, p = 0.696) and for men was 1.051 (95% CI 0.974–1.133, p = 0.204). Female sex is the most important genetic risk factors for GCA as reported above. Polymorphisms of the HLA II gene in particular the presence of HLA DRB1*04 alleles (both HLA DRB1*0401 and HLA DRB1*0404) are systematically associated with GCA supporting the thesis that GCA is driven by an antigen-based immune response.