“The Amish Experience”: More Exposure, Less Asthma

A recent study of children from two traditional, agrarian communities seems to indicate that environmental exposures experienced by Amish children dramatically reduce their predisposition to asthma. Previous statistics showed the prevalence of asthma among Hutterite children to be 21.3%, with allergic sensitization at 33.3%. Amish schoolchildren displayed dramatically lower rates, at only 5.2% and 7.2%, respectively. Seeking insight on the disparity, researchers compared the surroundings, genetics, and biology of 30 Amish children from Indiana with those of 30 Hutterite children from South Dakota.

Dust was collected from mattresses and floors of 10 homes in each community, and endotoxin levels from the Amish airborne dust were 6.8 times higher than found in Hutterite homes, with a higher proportion of the Amish homes evidencing common animal allergens. “The striking differences found in endotoxin levels support the notion that the Amish indoor environment is much richer in microbial exposures,” the authors write.

Genotypes of the children from both groups were graphed, and the overlap displayed striking genetic similarity. None of the Amish children in the study had asthma though, compared with 6 of the 30 Hutterite (20%). All of the youths were between 7 and 14 years old.

According to study co-author Carole Ober, "It shows that the source of protection is not simply farming.” In blood samples, the Amish children had markedly more neutrophils and fewer eosinophils, the former being blood cells that fight infections, the latter being blood cells that cause allergic inflammation.

The researchers modeled asthma in two sets of mice, one of which lacked proteins associated with innate immunity, and introduced the extracts of both types of dust to them. In the regular mice, the Amish dust produced less asthmatic responses than the Hutterite dust, but in the mice without MyD88 and Trif, the innate immunity genes, the effect disappeared. The authors say this highlights both “that products from the Amish environment are sufficient to confer protection from asthma,” and “the novel, central role that innate immunity plays in directing this process.”

The study, conducted by researchers from the University of Chicago and published in the New England Journal of Medicine, admits that its sample size was relatively small, and the inability to study children 6 years old and younger left out access to early stages of immune development. While it doesn’t necessarily provide a prescription for asthma prevention (“You can’t put a cow in every family’s house,” says Ober), this work does present new and fascinating leads for the future.