Supplement Article |
OP4. THE EPIDEMIOLOGY OF GIANT CELL ARTERITIS
Ipswich Hospital NHS Trust, UK
The incidence of GCA is highest in Scandinavia and populations of Nordic descent (e.g. Olmsted County, USA). The annual incidence in Scandinavia is 15–35/100,000 persons aged >50 years [1] and in Olmsted County 18.8/100,000 persons aged >50 years [2]. Studies from other regions of Europe report lower incidence rates. Multiple regression analysis suggests there is a significant trend to higher incidence with increasing latitude [1]. Some of the differences may reflect different diagnostic approaches in particular the biopsy rate and intensity of histological search for evidence of vasculitis. Many studies are hospital based and retrospective, and this will underestimate the incidence.
There have been few studies from non-white Caucasian populations. In Southern California a retrospective study from an ophthalmology unit of patients undergoing temporal artery biopsy [3] reported 19/66 white Caucasian patients had a positive biopsy, compared with 1/9 Asian, 0/40 Hispanic and 0/6 African-Americans. Few clinical details are provided and it is possible that referral bias might account for these results. A national survey from Japan reported a prevalence of 1.47/100,000 [4], considerably lower than European figures.
Several long-term studies have reported a steady increase in incidence [1]. In Olmsted County between 1950–54 and 1980–84 there was an increase from 6.7/100,000 to 28.5/100,000 persons aged >50 years. The rate then stabilized and has not risen further [2].