Increased Incidence of Type 1 Diabetes in the South of Spain

Recent studies, both within and outside Europe, of the incidence of type 1 diabetes in children have produced dissimilar results, although they generally agree on an important annual increase, especially in children <5 years of age (1). Data from Spain solely concerning the population of Catalonia (∼15% of the Spanish population) showed a stable incidence from 1990 to 1994, with 12.3 type 1 diabetic subjects per 100,000 children <15 years of age (2). We present data concerning the change in the incidence of type 1 diabetes in the population of the pronvince of Málaga (Andalusia) over a period of 19 years. These data are in contrast with those reported by EURODIAB for the Spanish population (3). Studies reporting the changes in the incidence of type 1 diabetes in children around the world fail to show data for Spain (4). We therefore believe that in addition to showing interesting results (5), our study provides data worth collecting for inclusion in other reports.

Málaga is situated in southern Spain and has a population of 1,260,560 inhabitants (3.2% of all Spain), with 237,000 children (18.8%) <14 years of age. This study of diabetes tendency was carried out with incidence data in this population from 1982 to 2000. All type 1 diabetic children <14 years of age diagnosed between 1 January 1982 and 31 December 2000 were included. We used the capture-recapture method to estimate the degree of ascertainment of the primary source, which was through hospital records. The secondary source was the data from the Málaga Diabetes Association. The incidence was calculated with 95% CI, assuming a Poisson distribution. Two models were used to evaluate the tendency over time. The first was a nonparametric linear correlation model, where the coefficient of regression was the mean relative increase of the yearly incidence. The second was a logistic regression model, calculating the odds ratio of the global model.

During the 19-year period, a total of 739 diabetic children <14 years of age were registered prospectively. The degree of ascertainment was 98.8%, and there was no significant variation during the period. The linear tendency for the change in the incidence is expressed by regression equation: incidence = 0.60 × year + 10.2 (R² = 0.62, P = 0.01).

The mean incidence during the whole period was 16.3 (15.1–17.4) per 100,000 (range 8.45–26.6); for 1990–1994 (the period published by EURODIAB), it was 16.7 per 100,000 (significantly greater than that for Catalonia), and for the last 5 years, it was 20.8 per 100,000. This latest figure reflects an area with a very high incidence of childhood type 1 diabetes. In a previous retrospective transverse study (6) from 1998 to 2000 in the provinces of Seville, Granada, and Málaga (3,850,000 inhabitants, 10% of the Spanish population), the mean incidence was 20.7 cases per 100,000, confirming the high incidence levels seen in the Málaga study. The latest data from the Catalonian register (1996–1998) show no significant change in incidence of type 1 diabetes (from 12.4 to 13.7 per 100,000).

Linear regression analysis of the tendency showed an annual increase of 3.15% (1.9–4.4), and logistic regression analysis showed an annual increase of 3.8% (2.4–5.2). This increase in type 1 diabetes in Málaga is similar to the mean reported for European countries (3.4%), but both the increase and the incidence are greater than that given for Spain in the EURODIAB study (3).