Exposure to microbes, like those in Amish homes, could protect against asthma

Traditional farming lifestyles, such as those practiced by the Amish in the U.S., can mitigate asthma and allergy risk factors, according to a new study in the New England Journal of Medicine.

That’s because “in the Amish, intense and presumably sustained exposure to microbes activates innate pathways that shape and calibrate downstream immune responses,” the researchers found.

In earlier studies, researchers saw that farming families in Europe had children who developed fewer allergy and asthma problems than children living in industrialized cities, indicating a mixture of environment and genetics determined children’s propensity for either issue. But the researchers wanted to find out if the type of farming made a difference in its protective role against such childhood disorders.

They studied 60 children between the ages of 7 and 14—30 of them were Amish children who live on single-family, traditional farms in Indiana, and 30 of them were Hutterite children who live on industrial-size communal farms in South Dakota. The research team looked at the asthma and allergy indicators in blood samples, the children’s genetic makeup and the dust composition of their homes.

The study authors found that none of the Amish children had asthma, while six (about 20 percent) of the Hutterite kids did. But the difference could not be explained by genetics alone—the two groups (which both originated in Europe) had “remarkable genetic similarities” when it came to asthma indicators. This lead researchers to look at possible environmental factors.

They found that Amish households tended to have more airborne animal allergens in the dust than the Hutterite households, at a rate of four in 10 Amish homes to one in 10 Hutterite homes. While endotoxins were detectable in every home catalogued, median levels were nearly seven times higher in the Amish homes. All of this means that the Amish children, who did not have asthma, were expose to allergens, airborne toxins and irritants at higher rates than the Hutterite children, some of whom did have asthma.

Additionally, the median levels of 23 specific cytokines were lower in the Amish kids than Hutterite. This difference could have also shown itself in the way the two groups’ similar genomes were expressed differently between the two groups of children.

Ultimately, through a confirmatory test done on mice (that found that exposure to Amish dust precipitated an innate immune response), the researchers concluded that being exposed to certain allergens helped activatre certain genes that could help protect against asthma and allergies.

“In the end, the novelty of our work lies in the identification of innate immunity as the primary target of the protective Amish environment, a finding supported by results obtained in both humans and mice,” the researchers explained. "Conversely, our work suggests that susceptibility to asthma may be increased when innate immune stimulation is weak."