Asthma

What is asthma?

Asthma is a common chronic condition that affects the airways (the breathing passage that carries air into our lungs). People with asthma experience episodes of wheezing, shortness of breath, coughing, chest tightness and fatigue due to widespread narrowing of the airways (National Asthma Council Australia 2019a).

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.

It is worth noting that it can be difficult to distinguish asthma from chronic obstructive pulmonary disease (COPD) because the symptoms of both conditions can be similar—both have obstruction to the airways, both are chronic inflammatory diseases that involve the small airways (Buist 2003). Although the current definitions of asthma and COPD overlap, there are some important features that distinguish typical COPD from typical asthma. For more information, see Chronic obstructive pulmonary disease (COPD).

In addition, clinical symptoms of asthma and bronchiectasis may overlap significantly as symptoms of cough, sputum and dyspnoea can occur in either asthma or bronchiectasis (Kang et al. 2014). Although these two diseases present several common characteristics, they have different clinical outcomes. Therefore, it is important to differentiate them at early stages of diagnosis, so appropriate therapeutic measures can be adopted (Athanazio 2012). For more information, see Bronchiectasis.

What causes asthma?

The fundamental causes of asthma are not completely understood. The strongest risk factors for developing asthma are a combination of genetic predisposition with environmental exposure to inhaled substances and particles that may provoke allergic reactions or irritate the airways, such as:

  • viral respiratory infections
  • indoor allergens (for example, house dust mites in bedding, carpets and stuffed furniture, pollution and pet dander)
  • outdoor allergens (such as pollens and moulds)
  • tobacco smoke
  • chemical irritants in the workplace
  • air pollution
  • strong odours, such as perfume.

Other triggers can include cold air, change in temperature, thunderstorms, extreme emotional arousal such as anger or fear, hormonal changes, pregnancy and physical exercise. Certain medications can also trigger asthma: aspirin and other non-steroid anti-inflammatory drugs, and beta-blockers (used to treat high blood pressure, heart conditions and migraine) (WHO 2017).

Thunderstorm asthma

Thunderstorm asthma can occur suddenly in spring or summer when there is a lot of pollen in the air and the weather is hot, dry, windy and stormy. People with asthma and/or hay fever need to be extra cautious to avoid flare-ups induced by thunderstorm asthma between September and January in Victoria, New South Wales and Queensland because it can be very serious (National Asthma Council Australia 2019b). In 2016, a serious thunderstorm asthma epidemic was triggered in Melbourne when very high pollen counts coincided with adverse meteorological conditions, resulting in 3,365 people presenting at hospital emergency departments over 30 hours, and 10 deaths (Thien et al. 2018). Following this event, a thunderstorm asthma forecasting system has been developed to give Victorians early warning of possible epidemic thunderstorm asthma events in pollen season (Victoria State Government 2019).

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) (ABS 2018).

Prevalence by age and sex

Based on the 2017–18 NHS, among those aged 0–14 asthma was more common among boys. Conversely, among those aged 25–34 and 45 and over asthma was more common among women. Prevalence was similar among males and females aged 15–24 and 35–44 (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 (Almqvist et al. 2007).

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

The bar chart shows the prevalence of asthma by different age groups 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.

Note: Asthma refers to people who self-reported that they were diagnosed by a doctor or nurse as having asthma (current and long-term).

Source: ABS 2019a (Data table).

Prevalence by Indigenous status

In 2018–19, 16% of Aboriginal and Torres Strait Islander people had asthma (an estimated 128,000 people), with a higher rate among females (18%) compared with males (13%) (ABS 2019b).

The prevalence of asthma among Indigenous Australians was 1.6 times as high as non-Indigenous Australians after adjusting for difference in age structure.

The difference in asthma prevalence between Indigenous Australians 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 group and Indigenous status, 2018–19

The bar chart shows the prevalence of asthma between Indigenous and non-Indigenous Australians in 2018–19. One in six (16%25) of Aboriginal and Torres Strait Islander people had asthma in 2018–19, with a higher rate among females (18%25) compared with males (13%25). 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.

Note: Asthma refers to people who self-reported that they were diagnosed by a doctor or nurse as having asthma (current and long-term).

Sources: ABS 2019a; ABS 2019b (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:

  • overall, the prevalence of asthma was highest for people living in the lowest socioeconomic area (13%) compared with those living in the highest socioeconomic area (10%)
  • prevalence for males and females varies by socioeconomic area.

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

The horizontal bar chart shows the prevalence of asthma in different regions and socioeconomic areas in 2017–18. Females 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, patterns of asthma prevalence varied by socioeconomic area for both males and females.

Notes

  1. Rates have been age-standardised to the 2001 Australian Standard Population as at 30 June 2001. Age groups: 0–14, 15–24, 25–34, 35–44, 45–54, 55–64, 65–74, 75+.
  2. Remoteness is classified according to the Australian Statistical Geography Standard (ASGS) 2016 Remoteness Areas structure based on area of residence.
  3. Socioeconomic areas are classified according to using the Index of Relative Socio-Economic Disadvantage (IRSD) based on area of residence.

Source: ABS 2019a (Data table).

How does asthma affect quality of life?

Asthma has varying degrees of impact on the physical, psychological and social wellbeing of people living with the condition, depending on disease severity and the level of control. 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 (Australian Centre for Asthma Monitoring 2004; Australian Centre for Asthma Monitoring 2011). Asthma is described as well-controlled when there are few symptoms and little reliever use (e.g. less than 2 days/week), and no night waking or limitation of activity. A survey conducted in 2012 of 2,686 Australians aged 16 years and over with current asthma found that asthma was not well-controlled in almost half (45%) of people. More than half of this group were not using a preventer inhaler, or were using it infrequently (Reddel et al. 2015).

In 2017–18, self-assessed health status among people with asthma aged 15 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 compared with people without asthma (11% and 23%, respectively), and more likely to describe themselves as having fair health compared with people without asthma (16% and 9.9%, respectively). Conversely, people with asthma were more likely to describe themselves as having poor health compared with people without asthma (7.4% and 3.0%, respectively) (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: Rates have been age-standardised to the 2001 Australian Standard Population as at 30 June 2001. Age groups: 15–24, 25–34, 35–44, 45–54, 55–64, 65–74, 75+.

Source: ABS 2019a (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 levels of psychological distress compared with those without asthma (15%25 and 8.7%25, respectively). Similarly, people with asthma were more likely to experience very high levels of psychological distress compared with those without asthma (11%25 and 3.4%25, respectively).

Notes

  1. Rates have been age-standardised to the 2001 Australian Standard Population as at 30 June 2001. Age groups: 18–24, 25–34, 35–44, 45–54, 55–64, 65–69, 70–74, 75–79, 80–84, 85+.
  2. 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.

Source: ABS 2019a (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 bodily pain compared with those without asthma (27%25 and 17%25, respectively). Similarly, people with asthma were more likely to experience severe bodily pain compared to those without asthma (11%25 and 5.4%25, respectively).

Notes

  1. Rates have been age-standardised to the 2001 Australian Standard Population as at 30 June 2001. Age groups: 18–24, 25–34, 35–44, 45–54, 55–64, 65–69, 70–74, 75–79, 80–84, 85+.
  2. Bodily pain experienced in the 4 weeks prior to interview.

Source: ABS 2019a (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 slightly less likely to be employed compared with those without asthma (73%25 and 77%25, respectively).

Note: Rates have been age-standardised to the 2001 Australian Standard Population as at 30 June 2001. Age groups: 15–24, 25–34, 35–44, 45–54, 55–64. 

Source: ABS 2019a (Data table).

Comorbidities

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