Abstract
Aims To determine if there is a worldwide seasonal pattern in the clinical onset of Typeβ1 diabetes.
Methods Analysis of the seasonality in diagnosis of Typeβ1 diabetes was based on the incidence data in 0β to 14βyearβold children collected by the World Health Organization Diabetes Mondiale (WHO DiaMond) Project over the period 1990β1999. One hundred and five centres from 53 countries worldwide provided enough data for the seasonality analysis. The incidence seasonality patterns were also determined for ageβ and sexβspecific groups.
Results Fortyβtwo out of 105 centres exhibited significant seasonality in the incidence of Typeβ1 diabetes (Pβ<β0.05). The existence of significant seasonal patterns correlated with higher level of incidence and of the average yearly counts. The correlation disappeared after adjustment for latitude. Twentyβeight of those centres had peaks in October to January and 33 had troughs in June to August. Two out of the four centres with significant seasonality in the southern hemisphere demonstrated a different pattern with a peak in July to September and a trough in January to March.
Conclusions The seasonality of the incidence of Typeβ1 diabetes mellitus in children under 15βyears of age is a real phenomenon, as was reported previously and as is now demonstrated by this large standardized study. The seasonality pattern appears to be dependent on the geographical position, at least as far as the northern/southern hemisphere dichotomy is concerned. However, more data are needed on the populations living below the 30th parallel north in order to complete the picture.