The epidemiology of biopsy-positive giant cell arteritis: special reference to changes in the age of the population.

Objective. The incidence of giant cell arteritis (GCA) increases with age. The aim of the present study was to investigate whether the increasing incidence of biopsyproven GCA in Goteborg, Sweden, could be explained in terms of a change in the age composition of the general population. Methods. All cases of biopsy-verified GCA between 1976 and 1995 were recorded. The annual incidence was calculated for women and men aged 50 yr or older and its relationship with the age composition of the general population was tested statistically. Results. There was a significant positive correlation between age and the risk of developing GCA. In the general population, there was a shift towards higher age; in 1976, the mean age of people 50 yr or older was 63.2 (men) and 65.0 (women), whereas in 1995 it was 65.0 (men) and 68.1 (women). After compensating for this, the incidence of biopsy-proven GCA still increased significantly. Moreover, for women aged 50 yr or older, the risk of developing the disease increased more among younger subjects than older ones. Conclusions. The increase in the incidence of biopsy-proven GCA between 1976 and 1995 could not be explained merely in terms of the increasing age of the general population. It is most probably related to an increase in the influence of other factors.