Objective: Giant-cell arteritis (GCA) incidence is reported to be rising. A cyclic pattern of annual incidence rates and seasonal variations were reported by several groups. However, such fluctuations were not observed by others. We examined both annual and seasonal rates of GCA over a period of 25 years in Jerusalem.
Methods: Charts of all patients diagnosed as GCA between 1980-2004 were reviewed. In 170 cases GCA was biopsy-proven. Thirty-six additional cases were included as they met the American College of Rheumatology GCA classification criteria. Data on the Jerusalem population throughout the study period was collected from the annual publications of the Israel Bureau of Statistics. Age- and sex-specific incidence rates per 100000 population aged>or=50 were calculated.
Results: For the whole period, the average age-adjusted incidence rate was 11.3 per 100000, and 9.5 for the biopsy-positive cases. The female: male ratio was 1.4:1. Cyclic fluctuations of GCA incidence with 3 distinctive peaks, 8-10 years apart, were observed. Altogether, there was no apparent increase in GCA incidence during this period. Seasonal variations were observed: in 192 patients we were able to estimate the time of onset of GCA symptoms. It showed a peak in the months of May and June, with the number of patients being twice as expected for this period (p<0.001).
Conclusion: GCA onset was more common in late spring and early summer, and fluctuations in GCA annual incidence with 3 distinctive peaks were observed during a 25-year period. These suggest infectious or other environmental etiology, however thus far no such agents were proven.