Background. Asthma mortality among young people varies widely between
different countries. Geographical differences in asthma prevalence are
also believed to exist, but evidence is sparse owing to the lack of m
ulticentre surveys using common protocols. A survey was conducted of 1
2-year-old children living in defined areas of New Zealand, Wales, Sou
th Africa and Sweden, in order to see whether asthma prevalence and mo
rtality rates in children show parallel differences. Methods. Question
naires enquiring about a history of asthma and respiratory symptoms we
re issued to the parent. The children performed a simple exercise chal
lenge test. Results. Information was obtained for 4353 children. A his
tory of asthma at any time was reported for 16.8% of children in New Z
ealand, 12.0% in Wales, 11.5% in South Africa and 4.0% of Sweden, and
a similar pattern was shown by several other indices of asthma (variou
s relevant symptoms, inhaler use, response to exercise challenge, and
asthma mortality at ages 5-19 years). In Sweden wheezing was negativel
y associated with pet ownership; elsewhere there was a positive (thoug
h non-significant) association. Cat ownership was highest in New Zeala
nd and lowest in Sweden. Conclusions. The prevalence of asthma in chil
dren shows geographical variation which is parallel to that of asthma
mortality, being high in New Zealand and low in Sweden. Differential e
xposure to animal allergens is a possible factor in this variation.