This is an interesting little study. (I haven’t ranked Diabetologia in the journal heirarchy, however).
Apparently the protective genes for Type 1 diabetes are not as protective as they used to be…………Also, the high risk genes for Type 1 diabetes are not as necessary– all while the incidence of Type 1 diabetes has increased 2.5 times in Finland in the last 40 years.
They theorize environmental pressure as the cause. Impossible as it is for some here to believe, the Finns must be way ahead of the USA since Type 1 diabetes is *not* a reportable disease here, and we have no incidence statistics, only things like “this town has not gotten any bigger than it used to be but we never had a pediatric endocrinologist in the past, and now we have two and you can’t get appointments with them they are so busy” and “When I was a teacher I never remember any kids with Type 1 diabetes and now I am a principal and it seems like there are a lot.”
Temporal changes in the frequencies of HLA genotypes in patients with Type 1 diabetes-indication of an increased environmental pressure?
The incidence of Type 1 diabetes has increased 2.5 times during the time period from 1966 to 2000 in Finland-a general trend seen in almost all developed countries that can only be explained by environmental
factors. The aim of this study was to test the possible effect of a changing environment on distribution of genotypes associated with disease susceptibility.
METHODS. HLA DRB1-DQA1-DQB1 genes and two diabetes-associated polymorphisms at IDDM2 and IDDM12 were analyzed. The frequencies of genotypes were compared between cases diagnosed with childhood-onset Type 1 diabetes during the period of 1939-1965 ( n=367) and those diagnosed between 1990 and 2001 ( n=736).
Chi-square statistics or the Fisher’s Exact test were used for the comparison of frequencies of analyzed haplotypes and genotypes in the two groups.
RESULTS. The frequencies of ( DR3) -DQA1*05-DQB1*02 and ( DR4)
-DQB1*0302 risk haplotypes and the high risk ( DR3)
-DQA1*05-DQB1*02/DRB1*0401-DQB1*0302 genotype were higher while proportion of patients carrying protective haplotypes-( DR15) -DQB1*0602 and ( DR1301)
-DQB1*0603-or protective genotypes was lower in patients diagnosed before 1965 as compared to those who developed disease after 1990.
No temporal variation was found in the frequencies of genotypes at IDDM2 and IDDM12.
CONCLUSION/INTERPRETATION.
Our data suggest that the need for genetic susceptibility to develop Type 1 diabetes has decreased over time due to an increasing environmental pressure and this results in a higher disease progression rate especially in subjects with protective HLA genotypes.