Rising Hygiene Standards Linked to Incidence of Diabetes

A new study suggests that the dramatic increase in the incidence of autoimmune diseases such as type 1 diabetes (T1D) and allergies in developed countries could be related to the rise in hygiene standards.

Researchers at the University of Helsinki Children’s Hospital (HUS; Finland) and other institutions participating in the European Union (EU)-funded Diabimmune project have been following approximately 7,000 children, with Finland, Russian Karelia, and Estonia contributing 2,320 children between 3 and 5 years of age each, and 320 babies (up to 3 months old) to the study. The study was carried out over a period of three years, from 2010 to 2013.

The study participants underwent a vast array of tests, with families responding to an extensive questionnaire covering the child’s home environment, contact with animals, diet, and a family history of predisposition to immune related diseases, such as allergies. The children were also subjected to a battery of tests including blood and stool samples, allergies, and even the presence of dust under the child’s bed were recorded.

The researchers observed that the annual incidence rate of T1D among children under the age of 15 years was almost six times lower in Russian Karelia than in Finland (7.4 versus 41.4/100,000 children) over a ten-year time period, despite very limited differences in the frequency of predisposing and protective human leukocyte antigen (HLA) genotypes in the background population. In the same series, Finnish schoolchildren had celiac disease five times more frequently than schoolchildren in Russian Karelia. Thyroid autoimmunity was also about six times more common among Finnish schoolchildren when compared to their peers in Russian Karelia.

The Finnish schoolchildren also had significantly higher levels of birch and cat-specific IgE, suggesting increased allergic sensitization. Altogether, allergic sensitization was detected in 22% of the children in Finland, compared to 6% of the children in Russian Karelia. In the same group of subjects, the frequency of microbial infections involving Helicobacter pylori, Toxoplasma gondii, hepatitis A, and enterovirus antibodies were all more frequent in Russian Karelia than in Finland, indicating that the Russian Karelian schoolchildren had experienced a considerably heavier microbial load by the age of 12 years.

“The rapid increase in incidence seen in most developed countries cannot be due to pure genetic reasons but must reflect changes in lifestyle and living environment and their interactions with predisposing genes,” said lead investigator HUS professor of pediatrics Mikael Knip, MD. “There is a strong association between the incidence of immune-mediated diseases and improving standard of living and hygiene.”

The project scientists now need to analyze the data as well as the tens of thousands of samples collected from the children to try to identify the bacteria involved, or if, in fact, it is the total number of infections rather than a specific germ that is the critical factor. Should the project find specific bacteria, this would open the prospect of developing preventive therapies involving the introduction of microbes through vaccines or probiotic additives to food products.

Increasing global urbanization, beginning at the turn of the 19th century, has resulted in the populations of many of the world's wealthier nations experiencing very little exposure to so-called “friendly” microbes that stimulate the immune system, due to diminishing contact with animals, feces, and soil. Other aspects of modern life, such as antibiotics, sanitation, clean drinking water, paved roads, and so on, also lead to lower rates of exposure to these microorganisms.

Related Links:
University of Helsinki Children’s Hospital
Diabimmune project