Giant cell arteritis is more prevalent in urban than in rural populations:results of an epidemiological study of primary systemic vasculitides in Germany

Objective. To investigate the period prevalences of primary systemic vascul itides (PSV) in urban and rural populations in northern and southern German y in 1994. Methods. Questionnaires were sent to all hospital departments, all physicia ns, health insurance providers and pension funds, reference laboratories fo r autoimmune diseases, and death registries in two catchment areas in north ern and southern Germany (combined population 875 983) to identify patients with PSV between 1 January and 31 December 1994. Each catchment area encom passed both an urban and a rural area. Each case was re-evaluated by the au thors by applying the definitions of the 1992 Chapel Hill Consensus Confere nce on the Nomenclature of Systemic Vasculitis. Results. A total of 180 PSV patients were identified. The overall prevalenc e of PSV was 216 cases per 1 000 000 inhabitants (95% confidence interval ( CI) 173-259) in northern Germany vs 195 (95% CI 153-236) in southern German y. The prevalence of PSV was two-fold higher in women than in men, and five -fold higher in people aged greater than or equal to 50 yr than in people a ged < 50 yr. The most frequent type of PSV was giant cell arteritis (GCA), with 87 cases per 1 000 000 in northern and 94 in southern Germany, followe d by Wegener's granulomatosis, with 58 and 42 cases respectively. In the po pulation aged <greater than or equal to> 50 yr the prevalence of GCA was 24 0 per 1 000 000 in northern and 300 in southern Germany. In both northern a nd southern Germany the prevalence of GCA in this older population was sign ificantly higher in urban than in rural populations (355 per 1 000 000 vs 1 15 in northern Germany (P <0.01) and 395 vs 220 (P <0.05) in southern Germa ny). The relative risk for the older urban population having GCA was 2.25-f old higher (95% CI 1.4-3.6) than in the rural population, and for the femal e population it was 4.7-fold higher in the urban than in the rural areas (9 5% CI 2.4-9.3). Conclusion. In both northern and southern Germany, GCA was significantly mo re prevalent in urban than in rural populations, especially among people ag ed greater than or equal to 50 yr and in women. It remains unclear whether this disparity was due to underdiagnosis of GCA in the rural regions associ ated with differences in the German health-care system in cities vs rural a reas. Further studies must examine the role of (chronic) exposure to the en vironmental factors characteristic of cities.