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Objectives: To compare clinical characteristics, treatment and prognosis of two population-based cohorts of patients with biopsy-proven giant cell arteritis (GCA) from Olmsted County, Minnesota, USA (Olmsted cohort) and the Reggio Emilia area, Northern Italy (Reggio cohort)., Methods: All patients residing in Olmsted County and the Reggio Emilia area with a new diagnosis of biopsy-proven GCA in 1986-2007 were retrospectively identified. Patients were followed from GCA diagnosis to death, migration or September 2011., Results: The study included 110 patients in the Olmsted and 144 in the Reggio cohort. Compared with the Olmsted cohort, patients from the Reggio cohort had longer duration of symptoms prior to diagnosis (median 1.4 months vs. 0.7, p<0.001) and were younger (mean 74.6 years vs. 77.8, p=0.002), more likely to have cranial symptoms (93% vs. 86%, p=0.048), permanent vision loss (21% vs. 6%, p=0.001) and systemic symptoms (67% vs. 46%, p=0.001). ESR and CRP were higher (mean 88 mm/h vs. 73, and 89.0 mg/L vs. 35.2, both p<0.001) in the Reggio cohort. Patients from the Olmsted cohort received a higher initial prednisone dose (mean 53.6 mg/day vs. 49.5, p=0.001). There were no differences in relapse rates, cumulative glucocorticoid (GC) dosages at 1, 2 and 5 years, and time to first GC discontinuation., Conclusions: Geographical, genetic and/or environmental factors may contribute to the different clinical features at onset of GCA observed in this study.

Objective: To investigate time trends in the incidence and survival of giant cell arteritis (GCA) over a 50-year period in Olmsted County, Minnesota., Methods: Using the unified record system at the Mayo Clinic, we identified all incident cases of GCA first diagnosed between 1950 and 1999. Incidence rates were estimated and adjusted to the 1980 United States white population for age and sex. The annual incidence rates were graphically illustrated using a 3-year centered moving average. Survival rates were computed and compared with the expected rates in the population., Results: There were 173 incident cases of GCA during the 50-year study period. Of these, 79% were women and the mean age at diagnosis was 74.8 years. The overall age- and sex-adjusted incidence per 100,000 persons 50 years of age or older was 18.8 (95% confidence interval [95% CI] 15.9-21.6). Incidence was higher in women (24.4; 95% CI 20.3-28.6) than in men (10.3; 95% CI 6.9-13.6). Incidence rates increased significantly over the study period (P = 0.017); in particular, a progressive increase was observed from 1950 to 1979; subsequently, no substantial increases in incidence rates were observed. A cyclic pattern of annual incidence rates was apparent, with evidence of 6 peak periods. Survival among individuals with GCA was not significantly different from that expected in the population (P = 0.80)., Conclusions: The incidence of GCA increased over the first 3 decades of the study, then remained stable over the last 20 years. The previously observed cyclic pattern of annual incidence rates was still apparent over a 50-year period. Overall survival in GCA was similar to that in the population.

Objective: To determine the frequency of a low erythrocyte sedimentation rate (ESR) in patients with giant cell arteritis (GCA) and evaluate their clinical features in a defined population., Methods: A total of 167 patients with GCA were identified in the population of Olmsted County, Minnesota, between the years 1950 and 1998 using methods described in previous studies. All fulfilled American College of Rheumatology criteria for GCA., Results: In 9 of the 167 patients the ESR was less than 40 mm/hour (Westergren method) at diagnosis. These patients had less frequent systemic symptoms and visual symptoms than the others. No patient with low ESR developed blindness. Other manifestations were similar in those with low and those with high ESR. The response of symptoms to prednisone treatment was within 1 week, and after a median of 25 days of therapy the median ESR dropped from 19 mm/hour to 3 mm/hour. The median duration of glucocorticoid therapy in the 9 patients was 21.5 months and median followup after diagnosis was 12.5 years. Over a long period of observation (median 44 years) in the 9 patients with low ESR, 9 inflammatory events other than GCA were observed in 7 patients. The ESR was normal in 7 of these 9 other events., Conclusion: A low ESR in active GCA is not a rare occurrence. Causes may include localized arteritis in some patients and an inability to mount an acute phase serologic response in others.

Objective: To investigate trends in the incidence of giant cell arteritis over a 42-year period in Olmsted County, Minnesota., Design: Population-based incidence study., Setting: Olmsted County, Minnesota., Methods: All incidence cases of giant cell arteritis first diagnosed between 1950 and 1991 were identified using the unified record system at Mayo Clinic. Age- and sex-specific incidence rates were calculated using the number of incidence cases as the numerator and population estimates as the denominator. Overall rates were age- and sex-adjusted to the 1980 United States white population. The annual incidence rates were graphically illustrated using a 3-year centered moving average., Results: Between 1950 and 1991, 125 Olmsted County residents (103 women and 22 men) were diagnosed with giant cell arteritis. The age- and sex-adjusted incidence per 100,000 persons 50 years of age or older was 17.8 (95% CI, 14.7 to 21.0); incidence was significantly higher in women (24.2 [CI, 19.5 to 28.9]) than in men (8.2 [CI, 4.8 to 11.6]). Age-specific incidence rates increased with age (P < 0.0001). The annual incidence rates increased significantly over the study period (P = 0.002) and appear to have clustered in five peak periods, which occurred about every 7 years. A significant calendar-time effect was identified; it predicted an increase in incidence of 2.6% (CI, 0.9% to 4.3%) every 5 years., Conclusions: Our observation of a regular cyclic pattern in incidence rates over time supports the hypothesis of an infectious cause for giant cell arteritis. Similar studies in other populations are needed to confirm our findings.

Objective: To determine the incidence, prevalence, and survival of polymyalgia rheumatica (PMR) over a 22-year period in Olmsted County, Minnesota., Methods: Using the unified record system at the Mayo Clinic for the Olmsted County population, we reviewed all medical records with a diagnosis of PMR from 1970 through 1991., Results: There were 245 (173 female; 72 male) incidence cases of PMR between 1970 and 1991. The average annual age- and sex-adjusted incidence of PMR per 100,000 population > or = 50 years was 52.5 (95% confidence interval [CI] 45.9-59.2), with a significantly higher incidence in females (61.7; 95% CI 52.3-71.2) than in males (39.9; 95% CI 30.7-49.2). The incidence varied over the period of observation, but no significant trends were found. The prevalence of PMR among persons > or = 50 years on January 1, 1992 was 6/1,000. There was a small but significantly increased survival rate among male PMR patients compared with the general population., Conclusion: Our data demonstrate that PMR is a common nonfatal disease in the elderly, the incidence and clinical manifestations of which have varied but remained relatively stable over the last 2 decades.