Increase in asthma could be
linked to loss of rural lifestyle
Less exposure to a rural lifestyle could be one of the reasons
why the prevalence of asthma is rising throughout the world and
in New Zealand.
According to an international report into asthma prevalence for
the World Health Organisation and the Global Initiative for Asthma
released today to coincide with World Asthma Day, New Zealanders
suffer asthma at three times the global rate. The report says about
5 percent of the global population suffer from asthma while the
rate among New Zealanders is 15 percent.
The report says the prevalence of the disease is rising - particularly
where populations are urbanising and adopting Western lifestyles
- but the basic reasons remain unclear.
Dr Jeroen Douwes, from Massey University’s Centre for Public
Health Research, says
research around the world suggests exposure to animals may play
a key role in protecting children against atopic, or allergic,
asthma, which accounts for about half of New Zealand asthma sufferers.
He is currently leading a research project to uncover whether the
same can be said for New Zealand children and what might be behind
“If there is an association between life on a farm and low
levels of allergic asthma in New Zealand then we can compare the
with the European work. We might then be able to exclude a number
of possible causes that are different from Europe and identify
what it is that might help prevent allergic asthma.”
He says research in other countries suggests that children raised
on livestock farms are more likely to be protected from allergic
asthma than those from cropping farms. Dr Douwes says the protective
effect appears to come from an immune-like response to micro-organisms,
particularly bacterial endotoxin. He says there is also a hypothesis
that drinking unpasturised milk and being exposed to lactobacilli
changes the gut flora, again leading to a higher level of protection
against allergic diseases. He says reduced exposure to these and
other micro-organisms may explain the increasing prevalence of
allergic asthma in western countries.
“In farming homes, where the family is in contact with livestock,
bacterial endotoxin levels are significantly higher than in non-farming
homes. In a healthy person exposure to endotoxins may induce non-allergic
symptoms but protect against allergic symptoms. The challenge is
to find a balance between the two.”
Dr Douwes is also leading another research project investigating
whether exposure to endotoxins later in life can result in a protective
affect in adults, or even reverse pre-existing allergies.