SPACE-TIME CLUSTERING IN INSULIN-DEPENDENT DIABETES-MELLITUS (IDDM) IN SOUTH-EAST SWEDEN

Using the method developed by Knox, space-time clustering was analysed in all 584 cases of insulin-dependent diabetes mellitus (IDDM) diagno sed between 1977-1990 and below the age of 16 from four paediatric dep artments in south-east Sweden. The catchment areas of these clinics fo rm a contiguous geographical area of 26 445 km2 with a total of 165 78 4 children aged 0-15 years. The annual incidence for the study period was 25.2 per 100 000 children aged 0-15 years with a statistically sig nificant incidence variation between the years; highest incidence in 1 983 (39.2) and lowest in 1977 and 1989 (18.9 and 20.7 respectively). I n the analysis, 30 different combinations of critical cutoff values we re used to define closeness in space and time of pairs of cases. Stati stically significant results were seen for several combinations with t he highest significance obtained for the cutoff values of 15 km and 7 months, respectively. This space-time clustering tended to be speciall y pronounced during the period with the highest incidence of IDDM, 198 1-1985. Our results indicate that space-time clustering exists in IDDM . These findings may support the hypothesis that infectious agents (po ssibly viral) give rise to a portion of IDDM.