To: T.J. Wilkin (2001) The accelerator hypothesis: weight gain as the missing link between Type I and Type II diabetes. Diabetologia 44: 914-921

Double or hybrid diabetes associated with an increase in type 1 and type 2 diabetes in children and youths

The increase in the incidence of type 1 diabetes (T1D), especially in children <5 yr of age, reported over the past decade can be attributed to changes in environmental factors (either quantitative or qualitative) rather than to an effect of genetic factors operating in such a short period of time. The notable increase in the incidence of type 2 diabetes (T2D) in children and adolescents is very likely the consequence of an increasing sedentary lifestyle and an increase in obesity, which has been occurring in developed countries. An increase in the number of children and adolescents with a mixture of the two types of diabetes has recently come to light (i.e., subjects who are obese and/or with signs of insulin resistance as well as positive for markers of autoimmunity to beta cells), although the epidemiological data supporting such a conclusion are sparse. Under the current classification, it is difficult to define the type of diabetes affecting these young subjects, who might be classified as T2D because they are obese and insulin resistant but also as T1D because of the presence of autoantibodies to beta cells. These subjects show an overlapping diabetes phenotype typical of both T1D and T2D, suggesting that the current classification of diabetes should be revised to take into account this new form of diabetes, which has been called 'double diabetes' or 'hybrid diabetes'. In this review, we report recent findings on the increasing rates of all forms of diabetes in the young population, including unpublished data collected in Russia.

The incidence of type 1 diabetes in the age group 0-39 years has not increased in Antwerp (Belgium) between 1989 and 2000: evidence for earlier disease manifestation

OBJECTIVE

A worldwide increase in the incidence of childhood type 1 diabetes has been observed. Because in various countries the majority of new type 1 diabetic patients are diagnosed in adulthood, we investigated whether the rising incidence of this disorder in children reflects a global increase in the incidence of diabetes or a shift toward earlier clinical presentation.

RESEARCH DESIGN AND METHODS

The incidence of type 1 diabetes presenting before age 40 years was prospectively measured in the Antwerp district over a 12-year period (1989-2000). The completeness of ascertainment was evaluated by the capture-recapture method. Trends in incidence during the study period were analyzed by Poisson regression.

RESULTS

The incidence of type 1 diabetes diagnosed before age 40 years remained constant over the 12-year period, averaging 9.9 cases per 100,000 individuals per year. The incidence was similar in both sexes under age 15 years, but a marked male excess was noted for adult-onset disease, in particular after age 20 years, resulting in a male-to-female ratio of 0.9 under age 15 years vs. 1.6 thereafter (P = 0.001). During the 12-year observation period, there was a significant tendency toward increasing incidence under age 15 years at the expense of a decreasing incidence between ages 15 and 40 years (P = 0.025). The annual increase in incidence averaged 1.8% under age 15 years and 5.0% under age 5 years (P = 0.06).

CONCLUSIONS

Our results indicate that in Belgium, the increasing incidence of childhood type 1 diabetes-especially for children under age 5 years-is not attributable to a global increase in disease incidence, but rather to earlier clinical manifestation. The results suggest that an environmental factor may preferentially accelerate the subclinical disease process in young diabetes-prone subjects.