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Can We Be 'Too Clean?' Exploring Resistance to Asthma Among Amish

  • Berwood Yost
  • Berwood Yost, director of the Center for Opinion Research and the Floyd Institute for Public Policy at Franklin & Marshall College, led the survey of Amish women's health. (Photo by Melissa Hess)

Exposure to certain environmental and social elements appears to reduce the likelihood of asthma, according to a recently released study based on survey data collected by Franklin & Marshall College.

The survey of Amish women's health led by Berwood Yost, director of the Center for Opinion Research and the Floyd Institute for Public Policy at F&M, led to the study, published in May 2014 in the American Thoracic Society Journal. "Biobehavioral Risk Factors for Asthma in the Amish and General Populations of Central Pennsylvania" compared the significantly low rates of asthma among the Amish to increasing rates among the general population, and examined factors that might contribute to those rates.

Yost conducted the survey and study in collaboration with Kirk Miller, the B. F. Fackenthal Jr. Professor of Biology and co-chair of F&M's public health program. Also assisting were two Penn State medical doctors who presented the results at a San Diego conference of the American Thoracic Society in May, and F&M alumnae Anne Dimmock '10 of Penn State Milton S. Hershey Medical Center and Kristen Walters '11 of Penn State University College of Medicine. Recent F&M graduate Zach Adams '14, the first public health major to graduate with honors in public health, also contributed to the project during his senior year.

In this interview, part of an occasional feature called Three Questions, Yost and Miller discuss how the project came about, what they discovered, and what comes next.

Question: What prompted this research?

Yost: With my staff here, and Kirk, we collected data on the general health of Amish women in 2004 and 2005. Since the Amish don't have phones, we consulted church directories. We then went to homes of the names we selected and conducted in-person interviews of 288 women. We did a phone survey of 2,002 non-Amish women in central Pennsylvania. Researchers at Penn State Hershey then came to us seeking specific data about asthma and wanted us to collaborate with them on a study. So, together we started looking at the data and noticed there was almost no asthma among Amish women compared to the general population. That's consistent with findings in other studies done in Indiana. We wanted to explore why.

There is a hypothesis that people who live on farms or in larger families or are exposed to potential disease are going to build a resistance. The hypothesis is that you can be too clean. So, we wanted to ask, if you put all these non-Amish women on a farm in a big house, would their asthma rates go down? If we created a sample of non-Amish that looks like our Amish sample, what would their rates be? We did propensity score matching to narrow down our samples so they looked alike. The idea is that you control for these things: whether they live on farm, household size, body mass index, diet and depression.

We essentially created a comparison group that was as Amish-like as possible. Accounting for these things, we found there is some evidence that the low rate of asthma is owed to the Amish lifestyle. Some of these things do seem to matter. Now, what else matters? That's what the next phase of our research will explore.

Q: What conclusions have you been able to draw?

Miller: Are there lifestyle factors that affect asthma, like living on a farm or living in a big family, and diet? The answer is yes, but we have to confirm that. The second question is: accounting for all these things, do the Amish still have a lower rate of asthma? One theory is the Amish's exposure to horses reduces their chances for asthma. Then there's the question: do farm dwellers who are not Amish experience the same low rates of asthma? There's the question of whether it's related to microbiomes, microorganisms that share our body in the gut or lungs. These have health implications that we are just starting to realize.

Researchers have recently discovered that eating yogurt relieves depression, so apparently bacteria in your gut affect your mood. It's possible that bacteria in your lungs could affect asthma. Are we too clean? Maybe, but on the other hand, rates of asthma among inner-city children are considerably higher, and the trigger seems to be cockroaches. Genetics could also be a factor. If we can separate the genetics from the cleanliness, that would be interesting.

Q: What is the next step for this project?

Yost: Kirk and I have designed the next phase's survey, which we will be doing in the fall. We're going to do a health assessment of Amish and Plain Mennonite men and women, asking, of course, about asthma and other factors. That could help answer some of the questions this study has raised. But the survey is important for another reason: There has never been a community health needs assessment among the Amish or Plain Mennonites.