Objective: To investigate the period prevalences of primary systemic vasculitides (PSV) in urban and rural populations in northern and southern Germany in 1994.
Methods: Questionnaires were sent to all hospital departments, all physicians, health insurance providers and pension funds, reference laboratories for autoimmune diseases, and death registries in two catchment areas in northern and southern Germany (combined population 875 983) to identify patients with PSV between 1 January and 31 December 1994. Each catchment area encompassed both an urban and a rural area. Each case was re-evaluated by the authors by applying the definitions of the 1992 Chapel Hill Consensus Conference on the Nomenclature of Systemic Vasculitis.
Results: A total of 180 PSV patients were identified. The overall prevalence 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 Germany. The prevalence of PSV was two-fold higher in women than in men, and five-fold higher in people aged > or =50 yr than in people aged <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, followed by Wegener's granulomatosis, with 58 and 42 cases respectively. In the population aged > or =50 yr the prevalence of GCA was 240 per 1 000 000 in northern and 300 in southern Germany. In both northern and southern Germany the prevalence of GCA in this older population was significantly higher in urban than in rural populations (355 per 1 000 000 vs 115 in northern Germany (P<0.01) and 395 vs 220 (P<0.05) in southern Germany). The relative risk for the older urban population having GCA was 2.25-fold higher (95% CI 1.4-3.6) than in the rural population, and for the female population it was 4.7-fold higher in the urban than in the rural areas (95% CI 2.4-9.3).
Conclusion: In both northern and southern Germany, GCA was significantly more prevalent in urban than in rural populations, especially among people aged > or =50 yr and in women. It remains unclear whether this disparity was due to underdiagnosis of GCA in the rural regions associated with differences in the German health-care system in cities vs rural areas. Further studies must examine the role of (chronic) exposure to the environmental factors characteristic of cities.