How do childhood diagnoses of type 1 diabetes cluster in time?

Abstract

Background: Previous studies have indicated that type 1 diabetes may have an infectious origin. The presence of temporal clustering-an irregular temporal distribution of cases--would provide additional evidence that occurrence may be linked with an agent that displays epidemicity. We tested for the presence and form of temporal clustering using population- based data from northeast England.

Materials and methods: The study analysed data on children aged 0-14 years diagnosed with type 1 diabetes during the period 1990-2007 and resident in a defined geographical region of northeast England (Northumberland, Newcastle upon Tyne, and North Tyneside). Tests for temporal clustering by time of diagnosis were applied using a modified version of the Potthoff-Whittinghill method.

Results: The study analysed 468 cases of children diagnosed with type 1 diabetes. There was highly statistically significant evidence of temporal clustering over periods of a few months and over longer time intervals (p<0.001). The clustering within years did not show a consistent seasonal pattern.

Conclusions: The study adds to the growing body of literature that supports the involvement of infectious agents in the aetiology of type 1 diabetes in children. Specifically it suggests that the precipitating agent or agents involved might be an infection that occurs in "mini-epidemics".

Figure 1. Weekly influenza hospitalisations by calendar period (California, 0–4 years).

Figure 2. Annual number of cases of type 1 diabetes at ages 0–14 years in Northumberland, Newcastle upon Tyne and North Tyneside by year of diagnosis.

Figure 3. Number of cases of type 1 diabetes at ages 0–14 years in Northumberland, Newcastle upon Tyne and North Tyneside by calendar month and period of diagnosis.