Asthma and other atopic diseases in Australian children
Australian arm of the International Study of Asthma and Allergy in Childhood
Colin F Robertson, Marita F Dalton, Jennifer K Peat, Michelle M Haby, Adrian Bauman, J Declan Kennedy and Louis I Landau
Objective: To determine the prevalence of asthma,
eczema and allergic rhinitis in Australian schoolchildren using the
protocol of the International Study of Asthma and Allergy in
Design: Questionnaire-based survey.
Setting: Melbourne, Sydney, Adelaide (in winter-spring, 1993) and Perth (in winter-spring, 1994).
Subjects: All children in school years 1 and 2 (ages 6-7 years) or in year 8 (ages 13-14 years), attending a random sample of 272 schools, stratified by age and city.
Main outcome measures: Parent-reported (for 6-7 year olds) or self-reported (for 13-14 year olds) symptoms of atopic disease in the previous 12 months, or ever; treatment of asthma; and country of birth.
Results: 10 914 questionnaires were completed for 6-7 year olds and 12 280 for 13-14 year olds (84% and 94% response rates, respectively). Prevalence of wheeze in the past 12 months was 24.6% for the 6-7 year olds and 29.4% for the 13-14 year olds, and, among 6-7 year olds, was significantly higher in boys (27.4%) than girls (21.7%). Children born in Australia were more likely to report current wheeze than those born elsewhere (6-7 year olds: odds ratio [OR], 1.82; 95% confidence interval [CI], 1.55-2.15; and 13-14 year olds: OR, 1.88; 95% CI, 1.68-2.11). Prevalences of current eczema and allergic rhinitis were 10.9% and 12.0%, respectively, for the 6-7 year olds, and 9.7% and 19.6%, respectively, for the 13-14 year olds. Asthma, eczema and rhinitis coexisted in 1.8% of 6-7 year olds and 2.8% of 13-14 year olds.
Conclusion: This study provides evidence that asthma prevalence in Australian schoolchildren is continuing to increase and is higher among Australian-born children than among those born elsewhere. Asthma, eczema and allergic rhinitis coexist to a lesser extent than expected. These results form the basis for future Australian and international comparisons.
There is now substantial evidence that the prevalence of asthma and
other atopic disorders is increasing worldwide.1,2 While the prevalence of asthma has
been documented in the past 30 years, variation in methods and lack of
uniform diagnostic criteria make direct comparison between studies
difficult. Little is known about the prevalence of the other atopic
disorders -- eczema and allergic rhinitis -- both throughout the
world and particularly in Australia.
The International Study of Asthma and Allergy in Childhood (ISAAC) is a collaborative project which has developed a standardised methodology to describe the prevalence and severity of asthma, rhinitis and eczema in children throughout the world.3 Such data will provide a framework for aetiological research into lifestyle, environmental and genetic factors affecting these disorders. Phase 1 of ISAAC is to determine the prevalence of the disorders throughout the world. Phases 2 and 3 will be more comprehensive, using more detailed questionnaires and objective measures to confirm the differences seen in Phase 1 and to identify important aetiological factors.
Our study was part of Phase 1 of ISAAC. It aimed to determine the prevalence of asthma and other atopic diseases in Australian schoolchildren, to determine the burden of atopic disease in this country, and to provide a basis for international comparison.
We used the protocol of ISAAC3
to survey two age groups: 6-7 year olds (school years 1 and 2) and 13-14
year olds (school year 8). Subjects were all children in the relevant
years of a random sample of primary and secondary schools. The sample
comprised about 10% of all government, Catholic and independent
schools in the metropolitan areas of Adelaide and Perth; the area
within a radius of 20 km from the GPO in Melbourne; the area within a
radius of 10 km from the GPO in Sydney for primary schools (school years
1 and 2); and the Western Region of Sydney for secondary schools
(school year 8). Previous studies have shown these areas of Sydney and
Melbourne to be representative of the metropolitan areas of these
A five-page questionnaire was issued by teachers for completion by parents of the 6-7 year olds, and by the 13-14 year olds in the classroom under examination conditions. The questionnaires contained the three standard ISAAC modules, asking about symptoms of asthma, eczema and allergic rhinitis3 (see Box 1 for definitions), an additional module about treatment of asthma, and two extra questions about the children's and mothers' country of birth. No translations were provided. If the first questionnaire was not returned by the 6-7 year olds, a second was issued. A second visit was made to the secondary schools, if necessary, to recruit students absent at the initial visit.
Data were analysed with the statistical package SPSS-X.9 Results were adjusted for cluster effect, and chi-squared tests were used to compare prevalences, while significance of odds ratios (OR) was assessed with 95% confidence intervals (CIs).
Details of schools and subjects surveyed are shown in Box 2; 201
primary schools and 71 secondary schools participated, comprising
7%-42% of schools in the sampling area; 9% of schools selected
declined to participate. A total of 12 952 questionnaires
were issued to the 6-7 years age group (response rate, 84%) and 13 078 to
the 13-14 years age group (response rate, 94%).
Prevalence of atopic diseases in the two age groups is shown in Box 3.
Prevalence of current wheeze was 24.6% for the 6-7 year olds (95% CI,
23.8-25.4), and 29.4% for the 13-14 year olds (95% CI, 29.1-29.7) (Box 3). In the younger group, current wheeze was significantly more
common in boys than in girls (OR, 1.36; 95% CI, 1.25-1.49), but this sex
difference was reversed in the older group (OR 0.82; 95% CI,
Figure 1 (below) compares the prevalence of atopic diseases between the four cities. For the 6-7 year olds, there was no significant difference in prevalence of current wheeze between cities, but for the 13-14 year olds prevalence was slightly higher in the western cities (Adelaide and Perth: 32.3%) than in the eastern cities (Sydney and Melbourne: 25.9%) (OR, 1.37; 95% CI, 1.26-1.48). There was a similar difference between west and east in percentage of 13-14 year olds who had had more than 12 episodes of wheeze per year (4.1% versus 3.1%) and who had attended the emergency department (3.5% versus 2.9%) (data not shown). The prevalence of current wheeze was generally higher in the older age group.
The spectrum of asthma among children who reported current wheeze is shown in Box 4. While most children in both age groups reported only one to three asthma episodes in the previous 12 months, 8.0% of 6-7 year olds and 12.2% of 13-14 year olds reported more than 12 episodes. Sleep disturbance due to asthma was common, with 11.2% of 6-7 year olds and 9.8% of 13-14 year olds reporting sleep disturbance on one or more nights per week. About 7% of both age groups reported a hospital admission for asthma in the previous 12 months.
Patterns of asthma treatment are shown in Box 5. Regular b2-agonists were taken as sole therapy by 5.5% of 6-7 year olds and 7.4% of 13-14 year olds with current wheeze, while regular inhaled steroids were taken by 21.1% of 6-7 year olds and 14.6% of 13-14 year olds, rising to 49.7% and 36.9% for those with more than 12 episodes per year. While overall 26.5% of 6-7 year olds with current wheeze and 15.8% of 13-14 year olds had a written asthma management plan, this increased to 46.5% and 25.9% in those who reported 12 or more attacks in the past 12 months. Most children attended a doctor at least once during a wheezy episode throughout the year, but only 42.2% of 6-7 year olds and 31.3% of 13-14 year olds visited a doctor for a regular check-up.
|Prevalence of current eczema did not vary significantly between the cities (Box 3). Eczema was less common in boys than in girls in both age groups (6-7 year olds: OR, 0.81; 95% CI, 0.72-0.92; 13-14 year olds: OR, 0.57; 95% CI, 0.51-0.65). Sleep disturbance due to itching was common among those with current eczema; it was reported to occur at least weekly by 7.9% of 6-7 year olds and 13.4% of 13-14 year olds, and at a lesser frequency by 27% of 6-7 year olds and 30.4% of 13-14 year olds.|
|The prevalence of current allergic rhinitis was significantly higher in Adelaide and Perth than in Sydney and Melbourne (6-7 year olds: OR, 1.62; 95% CI, 1.44-1.82; 13-14 year olds: OR, 1.53; 95% CI, 1.40-1.68). Like wheeze, rhinitis was more common in boys than girls in the younger group (boys versus girls: OR, 1.19; 95% CI, 1.06-1.33), while this sex difference was reversed in the older group (boys versus girls: OR, 0.64; 95% CI, 1.40-1.68). Among those with current rhinitis, 71% of 6-7 year olds and 76% of 13-14 year olds reported that it interfered with their daily activity to some extent (troublesome rhinitis), while 18.5% of 6-7 year olds and 19.1% of 13-14 year olds described this interference as moderate to "a lot".|
Atopic disease and country of birth
Children born in Australia were more likely to report current wheeze
than those born elsewhere (6-7 year olds: OR, 1.81; 95% CI, 1.54-2.14;
13-14 year olds: OR 1.89; 95% CI, 1.69-2.12). This trend was similar
for children whose mothers were born in Australia compared with those
whose mothers were born elsewhere (6-7 year olds: OR, 1.29; 95% CI,
1.18-1.42; 13-14 year olds: OR, 1.58; 95% CI, 1.45-1.71).
When children born outside Australia were analysed by region
of birth (United Kingdom, Central Europe, South-East Asia or the
Middle East), there was no difference in the prevalence of wheeze
Eczema and rhinitis were also more common in children born in Australia than those born elsewhere. For eczema the OR was 1.31 (95% CI, 1.06-1.63) for 6-7 year olds and 1.36 (95% CI, 1.14-1.61) for 13-14 year olds. For rhinitis, the OR was 1.79 (95% CI, 1.42-2.26) for 6-7 year olds and 1.5 (95% CI, 1.32-1.70) for 13-14 year olds.
The proportion of children born outside Australia was higher in the eastern cities among 13-14 year olds (23%) than in the western cities (15%). Similarly, the proportion of mothers born outside Australia was higher in the eastern cities (54%) than in the western cities (39%). When the odds ratio comparing prevalence of wheeze among 13-14 year olds in western versus eastern cities was adjusted for child's country of birth, it fell from 1.37 to 1.25 (95% CI, 1.15-1.36).
Interrelations of atopic diseases
|Figure 2 (below) shows the overlap of asthma, eczema and allergic rhinitis. While 35.2% of 6-7 year olds reported having at least one of these conditions in the past 12 months, only 1.8% reported having all three. Corresponding figures for 13-14 year olds were 41% with at least one condition and 2.8% with all three. Among those with current wheeze, only 19% of 6-7 year olds and 18% of 13-14 year olds reported coexistent current eczema, with no apparent age effect in the relationship.|
This study describes the burden of atopic disease in Australian
schoolchildren. The prevalence of current wheeze was similar to that
reported in recent epidemiological studies in Australia.10 However, comparison with results
of a similar questionnaire given to Melbourne schoolchildren in 1990
suggests that, although the spectrum of asthma remains unchanged,
the prevalence of recent wheeze has increased from 23.1% in 1990 (95%
CI, 21.7-24.5)4 to 27.2% in
1993 (95% CI, 25.6-28.8) (P < 0.01). The rate of increase
(1.4% per annum) is similar to that reported in an earlier Australian
study (1.24%)10 and higher
than that reported in European studies (0.1%-0.4%).1 |
Morbidity due to asthma remains significant, with high levels of symptoms, emergency department attendances and hospital admissions. Asthma is the second most common reason for admission to a paediatric hospital bed in Victoria (after otolaryngological conditions), with a rate in children of 738 per 100 000 population in 1994-1995.11 The total annual cost to the community associated with asthma management in Australia was estimated in 1989 as $627 million, or $769 per asthmatic person.12 These costs are likely to have increased because of the increases in medication costs and asthma prevalence.
There was a significant difference in the prevalence of current wheeze and current rhinitis between the eastern and western States. A possible explanation is the difference in patterns of immigration, with more children in the eastern cities born outside Australia than in the western cities. Indeed, the odds ratio comparing prevalence of wheeze among 13-14 year olds in western versus eastern cities fell from 1.37 to 1.25 after adjustment for country of birth.
Internationally, ISAAC has collected data on over half a million children from 120 centres in 48 countries. Australia ranks third-highest in prevalence of current wheeze for 13-14 year olds and second-highest for 6-7 year olds.13 For "current rhinitis", Australia ranks fifth and, for eczema, eleventh. Australia's high ranking for asthma prevalence is supported by data for asthma mortality. This was not collected by ISAAC, but comparison of available data from 11 developed countries shows Australia had the highest mortality rate due to asthma in 1990.14
We found evidence from throughout Australia for continuing lack of effective treatment of asthma. Among children with more than 12 episodes of wheeze per year, only 64% of 6-7 year olds and 43% of 13-14 year olds were taking regular preventive treatment. Further, 5.5% and 7.4% of those reporting "current wheeze" used regular b -agonists in the absence of any preventive therapy, despite the cumulative evidence against the practice. Sodium cromoglycate was used by 19% of the 6-7 year olds and 11% of the 13-14 year olds who reported taking regular preventive therapy, showing some support for the Australian paediatric asthma guidelines, which recommend cromoglycate as first-line therapy for mild to moderate persistent asthma.15
We also found eczema and rhinitis to be common and to cause significant morbidity among Australian schoolchildren. Eczema was less common in boys than in girls in both age groups, a trend seen throughout the world.16 It is not life-threatening, but may cause considerable physical and psychological disability (including discomfort from itching, which may result in sleep loss and secondary infection, as well as the psychological effects of a visible skin disease). Treatment can be expensive and time consuming. Recent Australian estimates of the cost to the family were $330 to $1255 a year, depending on eczema severity.17 Additional costs to the community for consultations ranged from $209 to $642 a year for each child.
Allergic rhinitis also carries significant morbidity. The effect on quality of life of perennial rhinitis has been estimated to be similar to, or worse than, mild to moderate asthma.18 In adults, hayfever is estimated to cause, on average, the loss of a third of a day from work each year, in addition to loss of productivity through symptoms or the sedating effects of some drug treatments.18 There are no precise estimates for the cost of therapy, as many sufferers do not consult a medical practitioner,8 and most treatment is available "over the counter".
The higher prevalence of "current wheeze" found among 13-14 year olds compared with 6-7 year olds should be interpreted with caution, as the respondents differed between the two groups (parents for the 6-7 year olds and the children themselves for the 13-14 year olds). In an earlier study of Melbourne 7-year-olds and 15-year-olds, in which parents completed the questionnaire for both age groups, prevalence of "current wheeze" was lower among the 15-year-olds (18.6%) than among the 7-year-olds (23.1%).4 Further, comparison of adolescent and parent responses to an Australian asthma morbidity questionnaire showed that the adolescents reported a higher incidence of symptoms than their parents.19
The correlation between the three atopic diseases was less than anticipated. Atopy is usually associated with increased serum levels of IgE and positive skin reactivity to common allergens and has a strong genetic basis. The factors that determine the phenotypic expression of atopy and direct it to asthma, eczema or hayfever are unclear. This diverse expression of the genotype needs to be considered when studying the genetics of asthma.
In conclusion, Australia has a high prevalence of atopic disorders, ranking among the highest in the world. Our study, part of a much larger international study, provides an opportunity to gain new insights into the causes and natural history of these disorders.
|We would like to thank the schools, parents and children who participated, the research assistants who helped collect the data, and the State departments of education that approved the study. In Adelaide, the study was supported by Rotary, in Perth by the Asthma Foundation of Western Australia, and in Melbourne and Sydney by internal department funds.|
Received 30 Oct 1997, accepted 10 Mar 1998
Authors' detailsDepartment of Thoracic Medicine, Royal Children's Hospital, Melbourne.
Colin F Robertson, MSc, FRACP, Deputy Director;
Marita F Dalton, Assoc Dip Med Rec, Research Assistant.
Department of Medicine, University of Sydney, Sydney.
Jennifer K Peat, PhD, Senior Research Fellow;
Michelle M Haby, MAppSc, Research Assistant.
School of Community Medicine, University of New South Wales, Sydney.
Adrian Bauman, PhD, FAFPHM, Associate Professor.
Department of Respiratory Medicine, Women's and Children's
J Declan Kennedy, MD, FRCP, Physician.
Department of Respiratory Medicine, Princess Margaret Hospital for
Louis I Landau, MD, FRACP, Professor of Paediatrics.
Reprints will not be available from the authors.
Correspondence: Dr C F Robertson, Department of Thoracic Medicine, Royal Children's Hospital, Flemington Road, Parkville, VIC 3054.
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<URL: http://www.mja.com.au/> © 1998 Medical Journal of Australia.
Received 18 November 2018, accepted 18 November 2018
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