Incidence rate and spatio-temporal clustering of type 1 diabetes in Santiago, Chile, from 1997 to 1998* Taxa de incidência e agrupamento espaço- temporal de diabetes tipo 1 em Santiago, Chile, de 1997 a 1998

Abstract ObjectiveTo estimate the incidence rate of type 1 diabetes in the urban area of Santiago,Chile, from March 21, 1997 to March 20, 1998, and to assess the spatio-temporalclustering of cases during that period.MethodsAll sixty-one incident cases were located temporally (day of diagnosis) and spatially(place of residence) in the area of study. Knox ’s method was used to assess spatio-temporal clustering of incident cases.ResultsThe overall incidence rate of type 1 diabetes was 4.11 cases per 100,000 childrenaged less than 15 years per year (95% confidence interval: 3.06 –5.14). The incidencerate seems to have increased since the last estimate of the incidence calculated forthe years 1986 –1992 in the metropolitan region of Santiago. Different combinationsof space-time intervals have been evaluated to assess spatio-temporal clustering.The smallest p-value was found for the combination of critical distances of 750meters and 60 days (uncorrected p-value = 0.048).ConclusionsAlthough these are preliminary results regarding space-time clustering in Santiago,exploratory analysis of the data method would suggest a possible aggregation ofincident cases in space-time coordinates.