- Recently an article in the New England Journal of Medicine
of a study based on data from Europe set off a minor media frenzy. The summary?
"Children living on farms were exposed to a wider range of microbes than were children in the reference group, and this exposure explains a substantial fraction of the inverse relation between asthma and growing up on a farm."
This is the epitome of Hygiene Hypothesis, which posits that our immune system is weakened because we are too clean and too "healthy." Sanitary homes deprive our kids of microbes to challenge their immune systems and toughen them up; overuse of antibiotics complicates matters by killing off whatever infections they get.
The immune system strikes back by reorienting itself to attack otherwise harmless things like peanut proteins or pollens with a toxic stew that evolved to fight parasites in less-hygienic times. Instead of attacking, say, hookworms, the antigen IgE goes after that peanut butter sandwich.
Proponents of the HH compare the prevalence of allergies in East and West Germany before and after unification. East Germany had more children growing up on farms and in larger families than West Germany, and much lower rates of allergies and asthma. Now, with its more westernized culture, East German rates of allergies and asthma have nearly caught up with West Germany.
It makes a great story. The whole farm-city thing resonates deep in the American mind. It evokes the mythic hold that farm life has over our national psyche. Farms good; cities bad. Wholesome Jeffersonian America is good for our children not only morally, but physically. The implication is that if we all grew up on farms, asthma wouldn't be at the epidemic levels we now have. Like something out of a Woody Allen
movie, it turns out we city parents sent our kids to the camp for the wrong reasons - we thought the air was fresh, and it turns out it was dirty.
However, I have trouble with this study for several reasons. First is that in medical science there are too many variables to draw sweeping conclusions from one set of data, and anyone who would do so is not a serious scientist, or is driven by an agenda (or both).
A case in point is a Forbes
blogger who took a pot shot at mold-inspired litigation against landlords, interpreting the study to mean that mold is good for us. He mentioned the case of Bianca Jagger
, who sued her landlord about mold growing in her Park Avenue apartment. Erin Brockovich
, Michael Jordan
, and Ed McMahon
are other celebrities who have coped with mold contamination, along with countless sufferers whose names are not familiar to us.
Some mold is, undoubtedly, good. Without it, we wouldn't have penicillin or blue cheese. But some mold can kill, particularly stachybotrys chartarum - a toxic black mold - which is often found in buildings with water damage. Other molds, while not immediately life threatening, are still potent allergens, including the ones you find in the woods behind the back 40, in Central Park, and in virtually any basement anywhere. Landlords don't get to decide which molds to allow in their properties as easily as deciding between Stilton or Roquefort. As for that wet laundry you left in the washing machine for two days, it may not make you sneeze, let alone kill you, but it does stink.
But while I object to using a specious inference to take a shot against the American tort bar, there are medical considerations to look at before we let the kids run barefoot through the barnyard as immunotherapy.
First, these were European farms under study. The European farm population may or may not be a fairly homogeneous group compared to city dwellers, and genetics make a large difference in who develops asthma. It stands to reason that generations of working the family farm may have bred a hearty cohort of kids who can breathe without wheezing.
Second, there may be something about European farming practices that makes their farm/city dynamic different from ours. European farms are regulated very differently from our own, in part because of the health fears of the European commissioners. For example, genetically modified food is much more tightly restricted in Europe, if it is legal at all. This means that Europeans use different fertilizers and pesticides than the ones we use here, which undoubtedly affects the rural health picture.
And European farm asthma may just be lagging behind ours. Typical farms are rampant with chemicals. Add to that the effects of earlier springs and longer summers on the pollen count because of climate change, and the aromatic plumes from manure lagoons, and no wonder rural America is suffering from an asthma epidemic that rivals the one we're seeing in urban America.
CDC researcher Dr. Teresa Morrison
, medical epidemiologist in the Air Pollution and Respiratory Health Branch, was lead author of an article in the Journal of Asthma
which concluded that "Asthma prevalence is as high in rural as in urban areas." The goal of their research is "To document patterns of asthma symptoms among rural residents in Midwestern states, and learn more about possible environmental exposures that potentially lead to asthma attacks."
David Van Sickle
, who has worked with Morrison, holds a doctorate from the University of Wisconsin, and is founder of a Madison-based company called Reciprocal Sciences. In a guest editorial for www.asthmaallergieschildren.com in November, he wrote that studies of farm workers in California showed that exposures to agricultural dusts were associated with the development of persistent wheeze, exposure to pesticides was associated with the development of asthma in women, and that community exposures to airborne waste from large scale animal agriculture might also be associated with exacerbations of asthma. As he also pointed out, this may have remained hidden because it's hard to study, but that is changing, in no small part because Van Sickle has developed an iPhone app called Asthmopolis, which can transmit information to doctors every time the patient - say a farmer - uses his inhaler.
No one who has studied immunology, as I have, can ignore the contribution farms have made to the treatment of the human immune system. As every biology student should know, vaccination began because Edward Jenner
noticed that milkmaids exposed to cow pox gained immunity from small pox.
However, I have my doubts that a similar benefit can be derived with asthma. Furthermore, as a clinician, I am concerned with helping my patients, and I doubt whether this information is going to help anyone's child in the foreseeable future. Maybe some of those farm microbes do have a salutary effect on kids' immune systems, but how exactly do we take advantage of it? Start a kibbutz movement for kids at risk of allergies and asthma? If I sound equivocal, it's because I am. Maybe sneezing, wheezing, and itching are the price we, both urban and rural, pay for "progress." So keep sending your kids to camp, but don't expect it to cure their asthma.