Asthma

What is asthma?

Asthma is a common chronic condition of the airways. People with asthma experience episodes of wheezing, shortness of breath, coughing and chest tightness due to widespread narrowing of the airways. The symptoms of asthma vary over time and may be present or absent at any point in time [1]. Asthma affects people of all ages and has a substantial impact on the community. In Australia, asthma accounted for 34% of the total burden of disease due to respiratory conditions and 2.5% of the total disease burden in 2015 [2]. In 2015–16, Asthma cost the Australian health system an estimated $770.4 million, representing 19% of disease expenditure for respiratory conditions and 0.7% of total disease expenditure [3].

The symptoms of asthma are usually reversible, either with or without treatment. The severity of asthma ranges from mild, intermittent symptoms, causing few problems for the individual, to severe and persistent wheezing and shortness of breath. In a few people with asthma, the disease has a severe adverse impact on quality of life and may be life-threatening.

While the underlying causes of asthma are still not well understood, there are a number of genetic, environmental and lifestyle factors that may increase the risk of developing asthma.

A number of factors can trigger asthma symptoms, and triggers may differ between individuals.

Triggers for asthma symptoms may include:

  • viral respiratory infections, such as colds
  • exercise
  • exposure to specific allergens (if a person is allergic to them) such as house dust mites, pollens, mould spores, pets and animals 
  • environmental irritants such as:
    • tobacco smoke and other air pollutants
    • cold/dry air
  • dietary triggers such as:
    • food chemicals/additives (if a person is intolerant)
  • medicines such as:
    • aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs)
  • occupational exposures to:
    • specific allergens
    • dust
    • fumes.

It can be difficult to distinguish asthma from chronic obstructive pulmonary disease (COPD) because the symptoms of both conditions can be similar—both are chronic inflammatory diseases that involve the small airways and cause airflow limitation [4]. Although the current definitions of asthma [5] and COPD [6] overlap, there are some important features that distinguish typical COPD from typical asthma. For example, people with COPD continue to lose lung function despite taking medication, which is not a common feature of asthma. More information and reports on COPD can be found under COPD.

There is increasing recognition of asthma-COPD overlap (also called asthma-COPD overlap syndrome, or ACOS). Overall, approximately 20% of patients with obstructive airway disease have been diagnosed with both asthma and COPD [7] (for more information on prevalence, see Asthma-COPD overlap 2017). It is important to identify people with asthma-COPD overlap, because they are at higher risk than patients with asthma or COPD alone, and because they should be treated differently from people with asthma or COPD alone [8]. The National Asthma Council Australia & Lung Foundation recently released an information paper on Asthma-COPD overlap, which includes recommendations for the treatment and management of the condition [8].

The National Asthma Strategy 2018 (the Strategy) was launched in January 2018. The Strategy aims to outline Australia’s national response to asthma and inform how existing limited health care resources can be better coordinated and targeted across all levels of government [9]. The Strategy identifies the most effective and appropriate interventions to reduce the impact of asthma in the community and continue to be an international leader in asthma prevention, management and research [9]. The AIHW will monitor and report on the outcome measures associated with The Strategy by reporting on the 10 national asthma indicators. For more information, see National Asthma Strategy 2018.

Who gets asthma?

Around 2.7 million Australians (11% of the total population) have asthma, based on self‑reported data from the 2017–18 Australian Bureau of Statistics (ABS) National Health Survey (NHS) [10]. In children, aged 5–14 years, asthma is a leading cause of total disease burden, contributing 14% of total burden for boys aged 5–14 and 12% of total disease burden for girls aged 5–14 [2].

Prevalence by age and sex

Based on the 2017–18 NHS, among those aged 0–14 asthma was more common among boys but among those aged 15–24 asthma was similar between males and females. Conversely, among those aged 25 and over (with the exception of the 35–44 years age group), asthma was more common among women (Figure 1). This change in prevalence for men and women in adulthood is likely due to a complex interaction between changing airway size and hormonal changes that occur during adolescent development, as well as differences in environmental exposures [11].

Figure 1: Prevalence of asthma, by age and sex, 2017–18

The bar chart shows the prevalence of asthma by different age group in 2017–18. For children aged 0–14 years, asthma was more common in boys (12%25) than in girls (8%25). However, for adults aged 25 and over, asthma was more common in females than in males. There was no difference in asthma prevalence between males and females among people aged 15-24 years.

Notes

  1. Age-standardised to the 2001 Australian Standard Population.
  2. Refers to people who self-reported that they were diagnosed by a doctor or nurse as having asthma (current and long-term).

Source: AIHW analysis of ABS 2019 [12] (Data table).

Prevalence by Aboriginal and Torres Strait Islander status

In 2012–13, 18% of Aboriginal and Torres Strait Islander Australians had asthma (an estimated 112,000 people), with a higher rate among females (20%) compared with males (15%).

The prevalence of asthma was almost twice as high among Indigenous Australians compared with non-Indigenous Australians (a rate ratio of 1.9) after adjusting for difference in age structure [13].

The difference in asthma prevalence between Indigenous and non-Indigenous Australians exists across all age groups, but is more marked for older adults (Figure 2).

Figure 2: Prevalence of asthma, by age and Indigenous status, 2012–13

The bar chart shows the prevalence of asthma between Indigenous and non-Indigenous Australians in 2012–13. The prevalence of asthma among Indigenous Australians was higher than that among non-Indigenous Australians in all age groups, but is more marked for older adults.

Source: Australian Aboriginal and Torres Strait Islander Health Survey (AATSIHS) 2012–13: First results, Table 6 (Data table).

Inequalities

The rate of asthma varies by remoteness and socioeconomic area.

For remoteness:

  • the variation for males was not significant
  • for females, the prevalence of asthma was highest for those living in Outer regional areas (15%) compared with those living in Major cities (11%).

For socioeconomic area:

  • Among males and females, the prevalence of asthma was highest for those living in the lowest socioeconomic area compared with those in the highest area (males: 13% and 10%, respectively; females: 16% and 9.9%, respectively).

Figure 3: Prevalence of asthma, by remoteness and socioeconomic area, 2017–18

The horizontal bar chart shows the prevalence of asthma in different regions and socioeconomic areas in 2017–18. Women living in major cities had a lower prevalence of asthma compared with those living in outer regional areas (11%25 and 15%25, respectively). Meanwhile, both men and women in lowest socioeconomic area had a higher prevalence of asthma compared with those in highest area (men: 13%25 and 10%25 respectively; women: 16%25 and 9.9%25 respectively).

 

Notes

  1. Remoteness is classified according to the Australian Statistical Geography Standard (ASGS) 2016 Remoteness Areas structure based on area of residence.
  2. Socioeconomic areas are classified according to using the Index of Relative Socio-Economic Disadvantage (IRSD) based on area of residence.
  3. Age-standardised to the 2001 Australian Standard Population.

Source: AIHW analysis of ABS 2019 [12] (Data table).

How does asthma affect quality of life?

Asthma is associated with poorer quality of life, with disease severity and the level of control both having an impact. Asthma has varying degrees of impact on the physical, psychological and social wellbeing of people living with the condition. People with asthma are more likely to describe themselves as having a poor quality of life. This is more pronounced among people with severe or poorly controlled asthma [14, 15]. Asthma is described as well-controlled when there are few symptoms and little reliever use (for example, less than 2 days/week), and no night waking or limitation of activity. A 2012 survey of 2,686 Australians aged 16 years and older with current asthma found that asthma was not well-controlled in 45% of people with current asthma. More than half of this group were not using a preventer inhaler, or were using it infrequently [16].

In 2017–18, self-assessed health status among people with asthma aged 15 years and over was, on average, worse than among those without asthma. For example, people with asthma were less likely to describe themselves as having excellent health (11% and 23%, respectively), and more likely to describe themselves as having fair (16% and 9.9%, respectively) or poor (7.4% and 3.0%, respectively) health compared with people without asthma (Figure 4).

Figure 4: Self-assessed health of people aged 15 and over with and without asthma, 2017–18

The bar chart shows the self-assessed health status among people aged 15 years and over with and without asthma in 2017–18. People with asthma in this age group were less likely to describe themselves as having excellent health (11%25 and 23%25, respectively), and more likely to describe themselves as having fair (16%25 and 9.9%25, respectively) or poor health (7.4%25 and 3.0%25, respectively), compared with people without asthma.

Note: Age-standardised to the 2001 Australian Standard population.

Source: AIHW analysis of ABS 2019 [12] (Data table).

In 2017–18, people with asthma were more likely to experience high (15%) and very high (11%) levels of psychological distress compared with those without asthma (8.7% and 3.4%, respectively) (Figure 5).

Figure 5: Psychological distress experienced by people aged 18 and over with and without asthma, 2017–18

The bar chart shows psychological distress experienced by people aged 18 and over with and without asthma in 2017–18. People with asthma in this age group were more likely to experience high (15%25 and 8.7%25, respectively) and very high (11%25 and 3.4%25, respectively) levels of psychological distress compared with those without asthma.

Notes

  1. Psychological distress is measured using the Kessler Psychological Distress Scale (K10), which involves 10 questions about negative emotional states experienced in the previous 4 weeks. The scores are grouped into Low: K10 score 10–15, Moderate: 16–21, High: 22–29, Very high: 30–50.
  2. Age-standardised to the 2001 Australian Standard population.

Source: AIHW analysis of ABS 2019 [12] (Data table).

In 2017–18, people with asthma were more likely to experience moderate (27%), severe (11%) and very severe (2.8%) bodily pain compared with people without asthma (17%, 5.4% and 1.3%, respectively) (Figure 6).

Figure 6: Pain experienced by people aged 18 and over with and without asthma, 2017–18

The bar chart shows pain experienced by people aged 18 and over with and without asthma in 2017–18. People with asthma in this age group were more likely to experience moderate (27%25 and 17%25, respectively), severe (11%25 and 5.4%25, respectively) and very severe (2.8%25 and 1.3%25, respectively) bodily pain compared with those without asthma.

Notes

  1. Bodily pain experienced in the 4 weeks prior to interview.
  2. Age-standardised to the 2001 Australian Standard population.

Source: AIHW analysis of ABS 2019 [12] (Data table).

In 2017–18, people aged 15 to 64 years with asthma were slightly less likely to be employed (73%) compared with people without asthma (77%) (Figure 7).

Figure 7: Workforce participation of people aged 15–64 with and without asthma, 2017–18

The bar chart shows workforce participation of adults aged 15–64 years with and without asthma in 2017–18. People with asthma in this age group were less likely to be employed (73%25 and 77%25, respectively) compared with those without asthma.

Note: Age-standardised to the 2001 Australian Standard population.

Source: AIHW analysis of ABS 2019 [12] (Data table).

Comorbidities

People with asthma often have other chronic diseases and long term chronic conditions. See Asthma, associated comorbidities and risk factors.

References

  1. National Asthma Council Australia 2019. Australian Asthma Handbook, Version 2.0. Melbourne: National Asthma Council Australia. Viewed on 1 May 2019. 
  2. AIHW (Australian Institute of Health and Welfare) 2019. Australian Burden of Disease Study 2015: Interactive data on disease burden. Cat. no. BOD 24. Canberra: AIHW.
  3. AIHW 2019. Disease expenditure in Australia. Cat. no. HWE 76. Canberra: AIHW.
  4. Buist AS 2003. Similarities and differences between asthma and chronic obstructive pulmonary disease: treatment and early outcomes, European respiratory journal 21(39 supplementary):30s–35s.
  5. GINA (Global Initiative for Asthma) 2019. Global Strategy for Asthma Management and Prevention.
  6. GOLD (Global Initiative for Chronic Obstructive Lung Disease) 2019. Global Strategy for the Diagnosis, Management and Prevention of COPD.
  7. Gibson PG & MacDonald VM 2015. Asthma-COPD overlap: now we are six. Thorax, 70:683-691.
  8. National Asthma Council Australia & Lung Foundation Australia 2017. Asthma-COPD overlap. Melbourne: National Asthma Council Australia.
  9. DoH (Department of Health) 2017.National Asthma Strategy 2018. Canberra: DoH.
  10. ABS (Australian Bureau of Statistics) 2018. National Health Survey: First Results, 2017–18. ABS cat. no. 4364.0.55.001. Canberra: ABS.
  11. Almqvist C, Worm M & Leyaert B 2008. Impact of gender on asthma in childhood and adolescence: a GA2LEN review. Allergy 63:47–57.
  12. ABS 2019. Microdata: National Health Survey, 2017–18, detailed microdata, DataLab. ABS cat. no. 4324.0.55.001. Canberra: ABS. Findings based on AIHW analysis of ABS microdata. 
  13. ABS 2013. Australian Aboriginal and Torres Strait Islander Health Survey: First Results, Australia, 2012─13. ABS cat. no. 4727.0.55.001. Canberra: ABS.
  14. ACAM (Australian Centre for Asthma Monitoring) 2004. Measuring the impact of asthma on quality of life in the Australian population. Cat. no. ACM 3. Canberra: AIHW.
  15. ACAM 2011. Asthma in Australia 2011: with a focus chapter on chronic obstructive pulmonary disease. Asthma series no. 4. Cat. no. ACM 22. Canberra: AIHW.
  16. Reddel HK, Sawyer SM, Everett PW, Flood PV & Peters MJ 2015. Asthma control in Australia: a cross-sectional web-based survey in a nationally representative population. Medical Journal of Australia 202:492–7.