Study objectives: The contribution of
atopy to childhood asthma has been debated. We aimed to examine the
relationship between atopy and asthma, taking into account differences
in respiratory symptoms and disease severity.
A cross-sectional asthma survey involving the following: (1) a
population sample of 758 (81% of eligible) school children aged 8 to
10 years from randomly selected schools in the Australian Capital
Territory in 1999, and (2) a hospital-based sample of 78 (70% of
eligible) children attending the hospital for asthma. Skin-prick test
results to 10 common aeroallergens were available on 722 children and
77 children, respectively. Baseline spirometry was obtained on a subset
of school children (n = 515, 78% of eligible).
Results: The association between atopy and wheeze by
wheeze frequency over the past year was as follows: no episodes (odds
ratio [OR], 1.00 [reference]), 1 to 3 episodes (OR, 3.27; 95%
confidence interval [CI], 2.15 to 4.97), 4 to 12 episodes (OR, 3.44;
95% CI, 1.75 to 6.75), and > 12 episodes (OR, 8.70; 95% CI, 3.07 to
24.55), with a higher population attributable fraction (PAF) for > 12
episodes (75%) than 1 to 3 episodes (49%). Atopy was moderately
related to asthma ever (OR, 2.09; 95% CI, 1.52 to 2.85; PAF, 33%) but
strongly related to 1999 hospital attendance for asthma (OR, 16.95;
95% CI, 6.76 to 42.48; PAF, 89%). Adjustment for child age,
gas heater use, and maternal smoking near the child did not materially
alter these findings.
Conclusions: The clinical
features of frequent wheeze or hospital asthma attendance are largely
attributable to atopy, but infrequent wheeze or a history of asthma
ever are not. Atopic children are overrepresented in the severe range
of the asthma spectrum.