Alan Adler, MD, from the Medical College of Wisconsin, and colleagues
sent 37,000 questionnaires to kindergarten through 12th grade school
children in rural Wisconsin school districts. They sought to compare
asthma prevalence in children who grew up on a farm to those who
lived in a non-farm rural area and to determine if the amount of
time the child lived on a farm was a factor. After compiling the
results of 4,152 completed surveys, researchers discovered:
> Children who grew up on a farm were significantly
less likely to have a history of wheezing or a diagnosis of asthma.
also reported less use of asthma medications.
> Asthma rates were higher in children who lived
on a farm only after age 5 compared to those who lived on a farm
age 5 and beyond.
> During the first 2 years of life, children
who grew up on a farm were less likely to report a history of
Researchers also found that children who lived on a farm were
significantly older, tended to have more siblings, were more frequently
breast-fed, and less likely to have attended daycare. All of these
factors have previously been shown to help reduce the development
of allergies and asthma.
In this study, asthma was consistently reported less frequently
among younger children who grew up on a farm, suggesting that exposures
occurring early in life have a more significant effect in modifying
asthma than those that occur later.
The JACI study was the first of its kind in the United States
to compare asthma prevalence in non-urban populations. The findings
coincide with similar studies completed in Europe, Australia and
Canada, which suggest that early exposure to elements unique to
a farm setting decrease the prevalence of asthma. However, the
current study suggests that the effects of the exposure may be
both time sensitive and time limited.