Asthma is a National Health Priority Area for Australia because it is a common chronic condition with a substantial impact on the community and with clearly defined interventions that can reduce its impact on individuals and the community. In comparison to other National Health Priority Areas in Australia, the prevalence of asthma is similar to that of injuries, moderately less than arthritis and cardiovascular diseases and higher than mental health problems, diabetes and cancer (Figure 1.1).
This report describes the status of asthma in Australia in 2005 using data from a wide range of sources. It aims to provide health professionals, health planners and policy makers, academics, consumers and interested readers with concise summaries of the latest available data and trends for asthma in Australia.
In this introductory chapter, we describe the characteristics of asthma and some of the difficulties inherent in measuring the disease in populations. We then outline the historical background from which this report has arisen and some of the activities that are in place to address asthma in Australia. The last part of this chapter provides an overview of the other sections of this report.
1.1 What is asthma? [back to top]
It has long been recognised that asthma is characterised by the presence of widespread, variable airflow obstruction and by the respiratory symptoms that accompany this. Over the last 10 to 20 years, there has been increasing recognition that the pathological changes underlying this physiological abnormality are characteristic and essential components of this entity. An important corollary of this understanding is that asthma is a chronic disease. Although it may have intermittent manifestations, it is most helpful to consider the disease in terms of the underlying chronic abnormality, rather than the intermittent or episodic manifestations.
The following descriptive ‘definition’ of asthma has been adopted by several international expert bodies since 1997: ‘Asthma is a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role, in particular, mast cells, eosinophils, T lymphocytes, macrophages, neutrophils and epithelial cells. In susceptible individuals this inflammation causes recurrent episodes of wheezing, breathlessness, chest tightness and coughing, particularly at night or in the early morning. These episodes are usually associated with widespread but variable airflow obstruction that is often reversible either spontaneously or with treatment. The inflammation also causes an increase in existing bronchial hyperresponsiveness to a variety of stimuli’ (DoHA: Li et al. 2002; GINA 2002; NAC 2002; National Asthma Education and Prevention Program 1997).
While this understanding of the nature of asthma enables clinicians, physiologists, pathologists, and epidemiologists to correctly identify many people with this disease, unfortunately it is not universally applicable. There are several theoretical and practical reasons for this:
Particular problems in distinguishing asthma from non-asthma arise in young children, where recurrent virus-associated wheeze and transient early wheeze (Martinez et al. 1998) have been described. Likewise, in the elderly, asthma and chronic obstructive pulmonary disease (COPD) can have similar symptoms and overlapping physiological abnormalities (Kennedy et al. 1990; Peat et al. 1987).
Types of asthma
It is clear that asthma is not a homogeneous disease entity. Several patterns have emerged. Historically, the methods of classifying asthma have reflected the existing disease paradigms.
Most existing guidelines classify patients with asthma as having intermittent or persistent asthma (NAC 2002; National Asthma Education and Prevention Program 1997; Warner & Naspitz 1998). It is not clear whether this distinction represents a fundamental characteristic of the illness, a marker of disease severity or, possibly, a marker of the periodical nature of exposure to triggers. The last may be partially true since intermittent asthma seems to be more common in children, where it is associated with viral infections (Johnston et al. 1995), and in regions where seasonal allergens play an important role as triggers for asthma (Boulet et al. 1983). Nevertheless, the distinction between intermittent and persistent asthma does appear to have long-term prognostic significance, as does the distinction between frequent and infrequent intermittent asthma (Phelan et al. 2002).
Studies of the natural history of asthma have revealed several longitudinal patterns of asthma. For example, the Tucson birth cohort study has identified ‘transient early wheeze’, which presents with symptoms before age 3 that remit before age 6, ‘late onset wheeze’, in which children develop wheeze after age 3 years, and ‘persistent wheeze’, a group of children who have wheeze before age 3 that persists at least until age 6 years (Martinez et al. 1998).
Asthma is also classified according to severity. However, many of the features of asthma are responsive to therapy, particularly with corticosteroids, and hence most ‘severity’ classifications are actually better described as assessments of disease control. Distinctions are necessarily arbitrary but most classifications are based on the presence and frequency of daytime and night-time symptoms, the frequency of need for bronchodilator (reliever medication), and the level and variability of lung function (NAC 2002; Reddel et al. 2000). Some classifications also incorporate information on the frequency and severity of disease exacerbations.
There are other subgroups among people with asthma that have been separately identified: for example, childhood asthma, exercise-induced asthma, aspirin-sensitive asthma and occupational asthma. While each of these groups has some features that distinguish it from other groups of people with asthma, there is no evidence that these distinctions represent fundamental characteristics of asthma.
Risk factors for asthma
While the underlying causes of asthma are still not well understood, there are several recognised factors that may increase the risk of developing the condition or trigger asthma symptoms in people who already have the condition. Risk factors for asthma may be broadly classified as:
Environmental and other related factors, such as diet and lifestyle, may:
There is a wide range of factors that trigger airway narrowing and symptoms in people with asthma, including exercise, viral infections, irritants (including smoking and indoor and outdoor air pollutants), specific allergens (for example, house dust mites and mould spores), and certain ingested food preservatives. In most cases, apart from viral infections and air pollutants, avoidance of exposure to these factors or control of symptoms before or after exposure is not particularly problematic for people with asthma. Apart from environmental tobacco smoke exposure in children and smoking in adults, which is an irritant exposure, this publication does not report on these factors.
The environmental causes of asthma have been extensively investigated and reviewed (NSW Health Department 1997; Peat 1994; Rural and Regional Health and Aged Care Services Division 2004). The subject remains controversial with conflicting evidence on the effects of exposure to pets and other allergen sources, the protective effects of breast-feeding and other aspects of diet and feeding, overweight and obesity, and the role of infections in childhood. A number of randomised controlled trials evaluating the effects of specific interventions for the prevention of asthma are currently underway. Without clear evidence of an important, avoidable causal role in asthma, these factors are not suitable targets for surveillance and have not been included in this report.
Exposure to occupational allergens has been conclusively linked both to the development of asthma, de novo, and to progression of the disease (Venables & Chan-Yeung 1997). Since this is a potentially avoidable cause of asthma, exposure to occupational allergens and the occurrence of occupational asthma are important targets for surveillance. Unfortunately, there are no comprehensive data on the incidence or prevalence of occupational asthma in Australia at the present time (Baker et al. 2004).
1.2 Responses to asthma in Australia [back to top]
Asthma has long been recognised as a major problem in Australia. In the late 1980s, health professionals, consumers and governments shared a common concern about rising morbidity and mortality attributable to this illness (Health Targets and Implementation Committee 1988; NHMRC 1988). Although inhaled corticosteroids had been available for the treatment of asthma since the early 1970s (Anon. 1972), it was not until around the late 1980s that compelling evidence of their effectiveness in the long-term treatment of asthma became available (Haahtela et al. 1991). Also at this time, consensus developed around the value of a systematic approach to asthma management and Australian respiratory physicians led the world in publishing a national asthma management plan (Woolcock et al. 1989).
It was against this background of rising concern about the problem of asthma, increasing awareness of the value of new approaches to treatment, recognition that information about these new approaches was not being disseminated or implemented, lack of strategies to inform people with asthma, and lack of national coordination that the National Asthma Campaign (NAC) was established (Pierce & Irving 1991). It arose as a collaboration between the Thoracic Society of Australia and New Zealand, the Royal Australian College of General Practitioners, the Pharmaceutical Society of Australia and the Asthma Foundations of Australia, with the aim of improving community awareness of the problem of asthma and promoting better asthma management according to the published guidelines (Woolcock et al. 1989). Among other initiatives, in 1988 the NAC undertook the first national public education campaigns, a mix of television and radio advertising, supported by substantial public relations activities in 1988 (Bauman et al. 1993), 1991, 1992, 1993 (Comino et al. 1997) and 2002 (Whorlow et al. 2003).
During the 1990s it became clear that the NAC’s National Asthma Strategy Goals and Targets could not be implemented without Australian Government support. In collaboration with many significant stakeholders in asthma, public health and government, the NAC worked to have asthma made a National Health Priority Area in 1999. Since then both the Australian and state governments have made a significant commitment to addressing the challenges by initiating a range of activities described in the following sections.
Australian Government initiatives
In 1999, Australian Health Ministers designated asthma as a National Health Priority Area. The National Health Priority Action Council and its expert advisory groups oversee the National Health Priority Areas initiative. The National Asthma Reference Group (NARG) is the expert advisory group for asthma.
The Asthma Management Program, which was announced in the 2001–02 Australian Government Budget, aimed at encouraging best practice asthma management. A major specific objective of the Program was to improve the quality of care provided by general practitioners to people with moderate to severe asthma. The four year Program is managed by the Department of Health and Ageing (DoHA).
Approximately two-thirds of the budget for the Asthma Management Program was allocated for payment of financial incentives, through DoHA’s Practice Incentives Program (PIP), to encourage GPs to implement the Asthma 3+ Visit Plan. The Plan involves a series of three GP visits by patients with moderate to severe asthma, for the purpose of diagnosis and assessment, patient education, and development and review of a written asthma action plan. The balance of the Program‘s funds has been made available for a range of other initiatives relating to the Asthma 3+ Visit Plan or to the broader objectives of the Asthma Management Program. These have included, for example:
• the Australian System for Monitoring Asthma;
Australian System for Monitoring Asthma
At the time of the commencement of the NHPA initiative for asthma, it was recognised that there was a need for a systematic approach to monitoring asthma in Australia. This had also been proposed in the NAC’s National Asthma Strategy Implementation Plan. Hence, the Australian Government Department of Health and Ageing funded the Australian Institute of Health and Welfare (AIHW) to establish and manage such a system, which was to include a national monitoring centre. The Australian Centre for Asthma Monitoring (ACAM) was established in February 2002 as a collaborating unit of the AIHW as part of what has become known as the Australian System for Monitoring Asthma (ASMA). ACAM is based at the Woolcock Institute of Medical Research, Sydney. The Centre aims to assist in reducing the burden of asthma in Australia by developing, collating and interpreting data relevant to asthma prevention, management and health policy.
ACAM’s tasks have included:
– consulting with a broad range of stakeholders about available asthma data and information needs through two series of state/territory workshops, in 2002 and in 2004;
In the future, ACAM will continue to work with data users and providers to further enhance the value of asthma monitoring data for their broad range of purposes. This may include recommendations for the measurement of new indicators and more detailed analyses of data as they become available.
State government asthma programs
Concurrently with the activities of the Australian Government, some state health authorities have implemented special projects to improve the management of asthma in their jurisdictions based on substantial advances in knowledge about the most effective management of this disease.
New South Wales
As a result of this review and advice from the Asthma Expert Advisory Group, a number of key projects have been funded including: the prevention, detection and surveillance of the disease burden arising from occupational asthma; introduction of training in Emergency Asthma Management for staff in disability residential services; smoking prevention projects in Indigenous communities; projects to improve the community care of people with asthma; and reducing hospital admissions for asthma, funded through the Primary Care Partnership (PCP) Strategy and the Hospital Admission Risk Program (HARP). The Victorian Health Information Surveillance System continues to monitor the prevalence and management of asthma in the Victorian population.
National Asthma Council Australia
In consultation with all relevant stakeholders the NAC and the DoHA are developing the National Asthma Strategy 2, which builds on the earlier National Asthma Strategy and the National Asthma Action Plan and indicates what still needs to be done to improve the community’s capacity to prevent asthma and care for people with asthma.
With funding from the DoHA, the NAC continues to provide a range of professional training and support to encourage the use of evidence-based methods of diagnosis and treatment for people with asthma. They are currently working through Divisions of General Practice to train GPs and practice nurses to support the Asthma 3+ Visit Plan and are conducting a virtual roadshow on childhood asthma management for GPs.
The NAC also make available a compendium of information, from consumer fact sheets to scientific reviews of the evidence related to asthma treatments (e.g. ‘Inhaled Corticosteroids: A Practical Perspective’ for GPs, pharmacists and asthma educators). This information is available in hard copy or via their website at <www.nationalasthma.org.au>.
Asthma Foundations of Australia
The Asthma Foundations of Australia is an association of state-based Asthma Foundations throughout Australia and provides programs and activities that work towards eliminating asthma as a major cause of ill-health and disruption within the community as well as educating people regarding optimum management of the condition.
An important highlight for the Asthma Foundations in 2004 was the ’Be Active for Asthma’ campaign, which promoted the message that asthma is a condition that can be successfully managed. It was launched for National Asthma Week in September 2004 with champion swimmer Sam Riley, who has had chronic asthma since childhood, as its patron.
The ‘Asthma Friendly Schools’ program focuses on education in the school environment about asthma symptoms and triggers and how to manage asthma. By the end of 2004, approximately 7,400 schools had registered in the program and become ‘asthma friendly’.
A currently planned activity is the ‘Asthma in older Australians’ project, which proposes to deliver a general awareness and education program throughout Australia over a 12-month period.
Another important service provided by the Foundations is the Asthma Information Line. This offers independent advice, education, counselling and support for people with asthma and their carers.
1.3 Overview of this report [back to top]
The complexity that underlies asthma poses major problems in identifying a single health surveillance definition for the disease. For some monitoring purposes there are limitations in the extent to which criteria used for the clinical diagnosis of asthma can be implemented. In particular, in cross-sectional surveys it is usually not possible to observe subjects at the time of disease exacerbations or examine changes over time, both of which are important elements in the clinical diagnostic process. On the other hand, in surveillance studies it is feasible to implement one or more criterion-based measurements and, hence, overcome much of the variability inherent in the clinical diagnostic process.
In the future, it is hoped that improved understanding of the nature of asthma, together with the evolution of data monitoring systems, will mean that the available data will accurately reflect the complex nature of this disease. For this present report, we have taken a pragmatic approach to evaluating and reporting the data that are currently available. While those data may not be ideal, we believe that, interpreted with due care, they do provide a valuable insight into the levels, trends and patterns relating to asthma in Australia in 2005.
The scope of this report is based on the indicator framework for asthma, initially proposed in August 2000 (AIHW 2000) and recently revised (Baker et al. 2004). In this report, we have included a focus chapter on asthma in children (Chapter 2). This draws together information from a range of sources to highlight the specific impacts of asthma in those aged 0 to 18 years. The remainder of the report contains data for all age groups on disease prevalence (Chapter 3), mortality (Chapter 4), health service utilisation (Chapter 5), asthma management including the application of asthma action plans, use of pharmaceuticals and measurement of lung function (Chapter 6), exposure to smoking and environmental tobacco smoke among people with asthma (Chapter 7), quality of life and markers of asthma control (Chapter 8) and expenditure on asthma (Chapter 9). The report describes recent time trends and seasonal patterns in these indicators and, where data are available, examines differences between age groups, between males and females, between socioeconomic groups, and between urban, rural and remote populations. Data for Aboriginal and Torres Strait Islander Australians and for people of culturally and linguistically diverse backgrounds are also presented where these are available. Finally, for some of the indicators, comparisons among states and territories and with selected overseas countries are described.
An outline of data sources, classifications and analysis methods is included in Appendix 1, and Appendix 2 contains statistical data tables. A full description of the data sources can be found in the report Review of Proposed National Health Priority Area Asthma Indicators and Data Sources (Baker et al. 2004), available at <www.asthmamonitoring.org>.
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