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 29% of the total burden of disease due to respiratory conditions in 2011 [2].

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 [3]. Although the current definitions of asthma [4] and COPD [5] 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 in the COPD snapshot.

There is increasing recognition of asthma-COPD overlap (also called asthma-COPD overlap syndrome, or ACOS), which affects around 15–20% of people with either diagnosis [6,7]. 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].

Who gets asthma?

11% of the Australian population have asthma.

Around 2.5 million Australians (11% of the total population) have asthma, based on self-reported data from the 2014–15 Australian Bureau of Statistics (ABS) National Health Survey (NHS) [9]. In children, aged 5─14 years, asthma is a leading cause of total burden, with asthma being the top ranked leading cause of total burden for male children aged 5─14 and the second leading cause of total burden for female children aged 5─14 [10].

Prevalence by age and sex

Based on the 2014–15 AHS, among those aged 0–14, asthma was more common in males, but among those aged 15 and over, asthma was more common in females (Figure 1). This change in prevalence for males and females after adolescence is likely due to a complex interaction between changing airway size and hormonal changes that occur during adolescent development. This change in prevalence for males and females after adolescence is likely due to hormonal changes during adolescent development and differences in environmental exposures [11].

Figure 1: Prevalence of asthma, by age and sex, 2014–15

The vertical bar chart shows the prevalence of asthma varied across age groups in 2014–15. Rates were highest at age 0–14 for males (12%25) and 45–59 (14%25) for females. From age group 15–29 onwards, females had consistently higher rates than males.

Note: Includes self-reported doctor-diagnosed current and long-term asthma.

Source: AIHW analysis of ABS Microdata, National Health Survey (NHS) 2014–15 (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 111,900 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 [12].

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 vertical bar chart shows that in 2012–13 Indigenous Australians had higher rates of asthma than non-Indigenous Australians across all age groups. Rates remained fairly steady for non-Indigenous Australians (at around 10%25), but increased with age for Indigenous Australians, peaking at 22%25 at age 55 and over.

Source: ABS 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 men this variation is not significant. However, in 2014–15, the prevalence of asthma in women was:

  • higher in Outer regional and Remote areas (15%) compared with Major cities (11%)
  • higher for those in the lowest socioeconomic group (15%) compared with those in the highest group (10%).

Figure 3: Prevalence of asthma, by remoteness and socioeconomic group, 2014–15

The horizontal bar chart shows that rates of asthma varied by remoteness and socioeconomic area in 2014–15. Asthma among women increased with increasing remoteness (11%25 in Major cities to 16%25 in Outer regional/Remote areas), however men in Outer regional/Remote areas had the lowest rates of asthma among all men (9%25). Rates of asthma decreased with increasing socioeconomic group for women (15%25 in Group 1 to 10%25 in Group 5), but rates for men were highly varied across the groups.

Notes:

  1. Age-standardised to the 2001 Australian Standard Population.
  2. Please see data table for information on remoteness and socioeconomic group classifications.

Source: AIHW analysis of ABS Microdata, NHS 2014–15 (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 report a poor quality of life. This is more pronounced among people with severe or poorly controlled asthma [13,14]. 

Asthma is described as well-controlled when there are few symptoms and little reliever use (e.g. less than 3 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 [15].

In 2014–15, self-assessed health was, on average, worse among people with asthma, compared with people without the condition. People with asthma were less likely to report excellent health, and more likely to report fair or poor health [9].

Figure 1: Self-assessed health among people with and without asthma, ages 15+, 2014–15

The vertical bar chart shows that in 2014–15 self-reported health was lower in people with asthma compared to those without – people with asthma were more likely to report having fair or poor health (24%25) when compared to their non-asthmatic counterparts (13%25).

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

Source: AIHW analysis of ABS Microdata: National Health Survey (NHS) 2014–15 (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 2016. Australian Asthma Handbook, Version 1.3. Melbourne: National Asthma Council Australia.
  2. Australian Institute of Health and Welfare (AIHW) 2017. The burden of chronic respiratory conditions in Australia: a detailed analysis of the Australian Burden of Disease Study 2011. Australian Burden of Disease Study series no. 14. BOD 15. Canberra: AIHW.
  3. Buist, A.S. 2003. Similarities and differences between asthma and chronic obstructive pulmonary disease: treatment and early outcomes, European respiratory journal 21 (39 supplementary):30s-35s.
  4. Global Initiative for Asthma (GINA) 2018. Global Strategy for Asthma Management and Prevention.
  5. Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2018. Global Strategy for the Diagnosis, Management and Prevention of COPD .
  6. Bateman ED, Reddel HK, van Zyl-Smit RN, Agusti A 2015. The asthma-COPD overlap syndrome: towards a revised taxonomy of chronic airways diseases? Lancet Respir Med; 3:719–28.
  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. Australian Bureau of Statistics (ABS) 2016. National Health Survey: First Results, 2014–15. ABS Cat no. 4364.0.55.001. Canberra: ABS.
  10. AIHW 2016. Australian Burden of Disease Study: Impact and causes of illness and death in Australia 2011. Australian Burden of Disease Study series no. 3. BOD 4. Canberra: AIHW.
  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 2013. Australian Aboriginal and Torres Strait Islander Health Survey: First Results, Australia, 2012─13. ABS Cat. no. 4727.0.55.001. Canberra: ABS.
  13. Australian Centre for Asthma Monitoring (ACAM) 2004. Measuring the impact of asthma on quality of life in the Australian population. Cat. no. ACM 3. Canberra: AIHW.
  14. 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.
  15. 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.