Epidemiology of biopsy proven giant cell arteritis in northwestern Spain: trend over an 18 year period

Objective-In Europe giant cell arteritis (GCA) is more common in Scandinavi an countries than in southern regions. Epidemiological studies on GCA in ot her more distant countries have indicated a progressive increase in inciden ce. A regular cyclical pattern in incidence of GCA over 20 years has been r eported in Olmsted County (Minnesota, USA). In contrast, no cyclical fluctu ation has been recently reported in Sweden. To investigate further the epid emiology of GCA in southern Europe the trend in incidence and fluctuations of this vasculitis over 18 years in the Lugo region of northwestern Spain w ere examined. Methods-A retrospective study of biopsy proven GCA diagnosed between 1 Janu ary 1981 and 31 December 1998 at a single hospital for a well defined popul ation of almost 250 000 people. Annual incidence was calculated for the who le group of patients and for men and women separately. Monthly variations, annual peaks of incidence, and trend in the incidence of biopsy proven GCA with and without polymyalgia rheumatica (PMR) were also examined. Results-One hundred and sixty one Lugo residents were diagnosed with biopsy proven GCA between 1981 and 1998. The average annual incidence for the pop ulation aged 50 and older was 10.24/100 000 (men 11.00?100 000, women 9.57/ 100 000). A progressive increase in the incidence in both men and women was seen. In men there was an annual increase of 8% (95% CI 4% to 13%; p<0.000 1). In women the annual increase was 11% (95% CI 5% to 17%; p<0.0001). The overall annual increase for men and women was 10% (95% CI 6% to 14%; p<0.00 01). No seasonal pattern or peaks in the incidence were seen. During the pe riod 1981-94 GCA was more common in men than in women. In contrast, during the last years of study the increase in incidence was higher in women. In w omen the annual ratio of incidence of GCA with PMR/incidence of GCA without PMR was generally higher than 1. However, in men the annual ratio was init ially 1 but decreased gradually, indicating a progressive decrease in the p roportion of men with biopsy proven GCA associated with PMR. Conclusion-In northwestern Spain there has been a progressive increase in G CA incidence. As seen in other countries where GCA is more common, during t he past few years the increase in incidence has been mainly due to a higher number of new cases in women.