CLUSTERING OF CHILDHOOD IDDM - LINKS WITH AGE AND PLACE OF RESIDENCE

OBJECTIVE - To improve understanding of the etiology of IDDM by analyz ing spatial and space-time distribution of the incidence in children. RESEARCH DESIGN AND METHODS - Statistical tests to detect clustering w ere applied to a population-based register of 1,490 children (aged 0-1 6 years) with IDDM in Yorkshire, northern England. The Knox test analy zed clustering in space and time, and the Potthoff-Whittinghill test q uantified spatial differences in incidence between small-area census u nits (electoral wards). The Potthoff-Whittinghill test was conditioned for childhood population density and deprivation (Townsend index). RE SULTS - Both tests demonstrated clustering of IDDM in Yorkshire childr en. Space-time and spatial clustering is strongest in the younger chil dren (0-4 and 5-9 years of age), even after conditioning for known ass ociations. Clustering was more common in the county of Humberside duri ng the years 1982-1985 and in wards of low population density (<0.26 0 - to 16-year-old subjects per hectare). CONCLUSIONS - The study reveal ed a nonrandom space-time distribution of IDDM in children not account ed for by known covarying demographic factors. The Potthoff-Whittinghi ll test has not previously been applied to childhood IDDM. The new fin ding of strong clustering in young children is consistent with early e xposure, possibly in utero, to infectious agents or localized environm ental sources.