NEW YORK -- May 22, 2008 -- Researchers report that the reason levels of type 1 diabetes have more than doubled in the past 25 years among Finnish children is likely due to a combination of genetic and lifestyle factors. The results are reported in this week's Diabetes Special Issue of The Lancet.
Based on a previous report that showed a steady increase in the incidence of type 1 diabetes in Finland between 1965 and 1996, Dr. Valma Harjutsalo, National Public Health Institute, Helsinki, Finland, and colleagues investigated present trends in the disease in Finland and predicted the number of children who will have it in the future.
The research team analysed 3 Finnish registers: the National Public Health Institute Diabetes Register, the Central Drug Register, and the Hospital Discharge Register, looking at the time period 1980 to 2005. Patients with type 2 diabetes were excluded, as were those with diabetes occurring secondary to other conditions, such as steroid use, Down's syndrome, and congenital malformations of the pancreas.
They found that 10,737 children -- 5,816 boys and 4,921 girls -- were diagnosed with type 1 diabetes before 15 years of age during 1980 to 2005. Incidence more than doubled in this period, from 31.4 per 100,000 in 1980 to 64.2 per 100,000 in 2005. In children aged 0 to 4 years, the increase was the largest, with an average annual increase of 4.7%. The overall boy-to-girl ratio of incidence was 1.1 to 1; at the age of 13 years, it was 1.7 to 1, and the incidence peak for girls (at 10 years) occurred 3 years before that for boys (at 13 years). Based on these data, the predicted cumulative number of new cases of type 1 diabetes before 15 years of age between 2006 and 2020 is around 10,800. Finland had exceeded its predicted 2010 incidence level by 2000.
The onset of type 1 diabetes is attributed to both genetic risk factors and environmental triggers. High birth weight and early weight gain in infancy have been implicated as risk factors for type 1 diabetes. Levels of obesity/being overweight in Finnish children have increased in past 2 decades and particularly in the past 10 years -- with the proportion of obese children between 5 and 15 years old rising from 9.5% in the mid-1980s to 20% now. The fall in birth weight over the same period emphasises the increased weight gain after birth. The authors concluded that "the incidence of type 1 diabetes continues to increase sharply in Finland, where it has been documented to be the highest in the world since the 1950s. Evidence does not support the theory that the increase results only from a younger age at onset of the disease. The steep increase in incidence noted in the last half of the 1990s might represent a serious signal about unhealthy changes in our everyday environment that affect the penetrance of type I diabetes susceptibility genes."
SOURCE: The Lancet
E-Mail this DGNews to a colleague
