Farm living could arm kids against asthma
Kids who grow up on traditional farms are 30% to 50% less likely than other children to develop asthma, a new study shows. But it's not the fresh country air.
It's the germs.
"Good" germs, that is, or at least harmless ones associated with cows, pigs and other barnyard creatures with which humans have been living, and maybe even co-evolving, for centuries.
Farm children whose household dust has the greatest variety of bacteria and fungi are much less likely to develop asthma and allergies than non-farmers, whose homes had fewer microscopic inhabitants, says the study of 933 European children in today's New England Journal of Medicine.
The study could help doctors better understand why childhood asthma rates have doubled in the past 30 years, says James Gern of the University of Wisconsin School of Medicine and Public Health, who was not involved in the study. About one in 10 U.S. children have asthma, according to the federal Centers for Disease Control and Prevention in Atlanta.
Though certain germs and microbes can make us sick, our bodies depend on others to function, says lead author Markus Ege of Munich University Children's Hospital in Germany.
Microbial cells make up about 90% of the cells in our bodies and help us perform basic tasks such as digesting food, Ege says.
But scientists can't explain precisely how farm germs protect against disease.
It's possible that they help "educate" the immune system by teaching the body what to attack and what to ignore, Ege says. Without this sort of education, immune cells may react to harmless things, such as pollen, and cause allergies.
It's also possible that in the germ-eat-germ world of our bodies, "good" microbes can muscle out "bad" ones, ridding the lungs of germs that might otherwise cause disease, Ege says.
"Maybe our immune system doesn't work quite as well when these microbes are missing," Gern says.
That country air
Farm kids: 4 to 8%
Non-farm kids: 10% to 12%
Farm kids: 12% to 25%
Non-farm kids: 39% to 41%
Source: New England Journal of Medicine
Though previous studies also have found lower rates of asthma in farm children, the new study provides the strongest details yet about which organisms create that protection — information that could help doctors prevent the disease, Gern says. Eventually, Ege says, doctors might be able to develop an asthma vaccine.
But he notes that taking suburban kids on an occasional field trip to the petting zoo probably isn't enough to build super-strong immune systems. For that, children — or even their mothers and grandmothers — may need to be exposed from an early age, Ege says. That might explain why asthma rates began increasing only relatively recently, even though people have been moving off farms for generations.
Still, that's no reason to stop cleaning the house, Ege says.
The kind of dust found in typical urban or suburban homes is very different from that found on farms. In fact, children living in dirty, roach-infested homes are at high risk for allergies, as are those exposed to diesel exhaust, says Jonathan Sperling, an allergy specialist at Children's Hospital of Philadelphia who was not involved in the study.
But it can't hurt for kids to spend more time outdoors and with animals, such as pets. "Just going outside is going to exercise your lungs," Sperling says.