Author Dr Penny Abbott
Expert reviewer Professor Anne Chang
Asthma is a chronic inflammatory disease of the airways that is characterised by variable and recurring symptoms of airway obstruction and bronchial hyper-responsiveness, often reversible spontaneously or with treatment. The predominant features of the clinical history are episodic difficulty in breathing and shortness of breath often accompanied by cough.54,55 After many years, the reversibility of airflow limitation may be incomplete in some people with asthma due to airways remodelling.55 Asthma is commonly known as ‘short wind’ in some Aboriginal and Torres Strait Islander communities.56
The diagnosis of asthma is a clinical one. When asthma is suspected on the basis of symptoms, spirometry, including reversibility testing, is the preferred initial test to determine the presence and severity of airways obstruction.57 Children over 7 years of age are usually able to perform spirometry. However, normal spirometry, particularly when the patient is not symptomatic, does not exclude asthma.56,57
Asthma affects 15% of Aboriginal and Torres Strait Islander people, compared to 10% of the non-Indigenous Australian population.58,59 Compared with non-Indigenous Australians, Aboriginal and Torres Strait Islander people have twice the rate of hospitalisation and three times the rate of death due to asthma.59,60 Surveys indicate that asthma is 1.5–4 times more prevalent in Aboriginal and Torres Strait Islander people residing in non-remote areas compared to those in remote areas.60,61
A long term solution to decreasing the burden of asthma may be early detection and prevention.62,63 However at this time few measures can be recommended for the prevention of asthma, as the underlying causes and the development of the disease are complex and incompletely understood.54
What is meant by the prevention of asthma can be variable, with the terms primary and secondary prevention sometimes being used when referring to prevention of symptom exacerbations in people with an existing diagnosis of asthma through early treatment of exacerbations or long term control of disease.54,56 However, for the purposes of this review, the literature definitions of prevention of asthma have been followed. Primary prevention of asthma is defined as prevention of the onset of asthma and secondary prevention is defined as intervention(s) for infants and children who are at high risk for the development of asthma due to the presence of atopic disease but who have not yet developed asthma symptoms or signs.56,57,64 An exception to this is the primary prevention of occupational asthma through avoidance of asthma- causing agents in the work place.54,65
It is accepted that environmental and lifestyle factors interact with genetic factors, such as an allergic tendency, to increase the risk of developing asthma.60,66,67 There is uncertainty about how to reliably predict an increased risk of asthma.54-56,62,67 Risk factors include a family history (particularly maternal) of asthma and allergies, and a past history of allergies in early life.63,64 Other risk factors for asthma that have been identified in observational studies are obesity, environmental pollution, work related exposures and diet.55,57 For people with high risk occupations, the presence of new onset rhinitis is associated with increased risk for occupational asthma.56
Interventions to decrease the risk of developing asthma
The most important and modifiable risk factor to reduce asthma is exposure to environmental tobacco smoke (ETS).57,60,68–70 Interventions to reduce ETS exposure may reduce the risk of childhood asthma and later persistent asthma.55–57 This is of particular importance given the high rates of ETS exposure for Aboriginal and Torres Strait Islander children both in utero and after birth.60
There is currently little evidence to support preventive strategies to reduce the development of asthma except for avoidance of environmental tobacco smoke and avoidance of asthma causing agents in the workplace.60 There is conflicting evidence on the effects of exposure to pets and other allergen sources, the protective effects of breastfeeding and other aspects of diet and feeding in preventing childhood asthma.60
Sensitisation to allergens, such as house dustmite and cats, is associated with asthma, but interventions to reduce exposure to these allergens have not been shown to prevent asthma.66,67,71 Allergen specific immunotherapy may be effective in preventing asthma in children with seasonal allergies,67 though more studies are needed before this can be recommended as a wider strategy for prevention of asthma.57
The effect of breastfeeding on childhood asthma is controversial. Although there are many other health related benefits from breastfeeding, there does not appear to be any persistent effect of breastfeeding on asthma rates.56,70
A diet high in fruit and vegetable intake has been shown to be associated with less asthma in children and adults in observational studies.57,72 Other dietary interventions have not been shown to be effective in preventing asthma. Ineffective interventions include infant feeding with soy formulae73 and the avoidance of commonly allergenic foods during pregnancy and lactation or in infant diets.56,70 There is insufficient evidence that dietary supplements for mother or infant with probiotics, fish oil or antioxidants are of benefit in reducing childhood atopy or asthma.56,57,74–76
Similarly, there is insufficient evidence that avoidance of airborne allergens in the home and measures to reduce exposure to dustmite decrease the rates of asthma or wheeze in young children.56,57,64 Further, there is no evidence that house dustmite control prevents asthma exacerbations.71 Long term treatment with antihistamines does not reduce the risk of asthma developing in children with atopic dermatitis, including those who are sensitive to house dustmite and/or grass pollen.56 Immunotherapy may reduce asthma risk in children with seasonal rhinoconjunctivitis,56,67,77,78 however more studies are needed before this can be recommended as a preventive strategy for asthma.57
Reducing exposure to potential environmental factors including allergens in the workplace may decrease a worker’s risk of developing asthma in the workplace. Reduction in exposure levels including the use of respiratory protective equipment reduces but does not eliminate the risk of occupational asthma.56,79,80
|Preventive intervention type||Who is at risk?||What should be done?||How often?||Level/strength of evidence|
||Routine screening for asthma is not recommended
Early detection strategies should be considered (eg. clinical vigilance, detailed history considering mimics of asthma, and spirometry when symptoms are suggestive)
||Maternal dietary restrictions during breastfeeding or pregnancy are not recommended for the prevention of asthma
||A high intake of fruit and vegetables should be recommended to those with or at risk of asthma*
||Children with seasonal rhino-conjunctivitis
||Advise that immunotherapy is not currently recommended as a preventive strategy of asthma
||Strategies to provide a smokefree environment are recommended
Smoking cessation advice should be given to pregnant and breastfeeding women (see Chapter 9: Antenatal care)
|Advise families that avoidance of exposure to airborne allergens such as house dustmite or pets is not shown to be effective in preventing asthma
|Workers in high risk workplaces, where exposure to occupational dusts and chemicals are likely
||Recommend use of respiratory protective equipment
|* Risk factors include a family history (particularly maternal) of asthma and allergies, a past history of atopy and food allergies in early life, obesity, low birthweight, in utero tobacco exposure, tobacco smoking, environmental tobacco smoke, environmental pollution and work related exposures55,57,63,64,81
British Guideline on the Management of Asthma (British Thoracic Society, Scottish Intercollegiate Guidelines Network)
Multiple resources including guides to asthma management and spirometry (National Asthma Council Australia)
International evidence based guidelines and clinical resources (Global Initiative for Asthma)
- Global Initiative for Asthma. Global strategy for asthma management and prevention. GIA, 2009.
- National Asthma Education and Prevention Program: Third Expert Panel on the Diagnosis and Management of Asthma. Expert panel report 3 (EPR3): guidelines for the diagnosis and management of asthma. Bethesda, MD: National Heart, Lung, and Blood Institute, 2007. Cited October 2011. Available at www.nhlbi.nih.gov/ guidelines/asthma/asthgdln.htm.
- National Asthma Council Australia. Asthma management handbook. Melbourne: National Asthma Council Australia, 2006. Cited October 2011. Available at www.nationalasthma.org.au/ cms/index.php?option=com_content&task=view&id=214&Itemid=287.
- Scottish Intercollegiate Guidelines Network. British guideline on the management of asthma. Guideline no. 101. SIGN, 2009. Cited October 2011. Available at www.sign.ac.uk/pdf/sign101.pdf.
- Australian Bureau of Statistics. National Aboriginal and Torres Strait Islander Health Survey, 2004–2005, cat. no. 4715. Canberra: ABS, 2006.
- Australian Institute Health and Welfare & Department of Health and Ageing. The health and welfare of Aboriginal and Torres Strait Islander peoples 2008. Canberra: AIHW, 2008. Cited October 2011. Available at www.aihw.gov.au/ publication-detail/?id=6442468085.
- Australian Centre for Asthma Monitoring. Asthma in Australia 2008. Canberra: AIHW, 2008.
- Thomson N, MacRae A, Burns J, et al. Overview of Australian Indigenous health status. HealthInfoNet, April 2010. Cited October 2011. Available at www.healthinfonet.ecu.edu.au/ health-facts/overviews.
- Szefler SJ. Advances in pediatric asthma in 2009: gaining control of childhood asthma. J Allergy Clin Immunol 2010;125(1):69–78.
- Sly PD, Boner AL, Bjorksten B, et al. Early identification of atopy in the prediction of persistent asthma in children. Lancet 208;372(9643):1100–6.
- Canadian Medial Association Journal. Prevention strategies for asthma – secondary prevention. CMAJ 2005;173(6 Suppl):13.
- Quint J, Beckett WS, Campleman SL, et al. Primary prevention of occupational asthma: identifying and controlling exposures to asthma-causing agents. Am J Ind Med 2008;51(7):477–91.
- Maas T, Kaper J, Sheikh A, et al. Mono and multifaceted inhalant and/or food allergen reduction interventions for preventing asthma in children at high risk of developing asthma. Cochrane Database Syst Rev 2009;Jul 8;(3):CD006480.
- Gaffin JM, Phipatanakul W. The role of indoor allergens in the development of asthma. Curr Opin Allergy Clin Immunol 2009;9(2):128–35.
- Canadian Medial Association Journal. Prevention strategies for asthma: primary prevention. CMAJ 2005;173(6 Suppl):S20–4.
- Arshad SH, Kurukulaaratchy RJ, Fenn M, Matthews S. Early life risk factors for current wheeze, asthma, and bronchial hyperresponsiveness at 10 years of age. Chest 2005;127(2):502–8.
- Subbarao P, Mandhane PJ, Sears MR. Asthma: epidemiology, etiology and risk factors. CMAJ 2009;181(9):E181–E90.
- Gotzsche PC, Johansen HK. House dustmite control measures for asthma. Cochrane Database Syst Rev 2008;Apr 16;(2):CD001187.
- Romieu I, Varraso R, Avenel V, Leynaert B, Kauffmann F, Clavel-Chapelon F. Fruit and vegetable intakes and asthma in the E3N study. Thorax 2006; 61(3):209–15.
- Osborn DA, Sinn JKH. Soy formula for prevention of allergy and food intolerance in infants. Cochrane Database Syst Rev 2006;Oct 18;(4):CD003741.
- Thien FCK, De Luca S, Woods RK, Abramson MJ. Dietary marine fatty acids (fish oil) for asthma in adults and children. Cochrane Database Syst Rev 2000(4):CD001283.
- Ozdemir O. Any benefits of probiotics in allergic disorders? Allergy Asthma Proceedings 2010;31(2):103–11.
- Osborn DA, Sinn JKH. Probiotics in infants for prevention of allergic disease and food hypersensitivity. Cochrane Database Syst Rev 2007;Oct 17;(4):CD006475.
- Jacobsen L, Niggemann B, Dreborg S, et al. Specific immunotherapy has long-term preventive effect of seasonal and perennial asthma: 10-year follow-up on the PAT study. Allergy 2007;62(8):943–8.
- Cox L, Nelson H, Lockey R, et al. Allergen immunotherapy: a practice parameter third update. J Allergy Clin Immunol 2011;127(1 Suppl):S1–S55.
- Tarlo SM, Liss GM. Prevention of occupational asthma. Current Allergy & Asthma Reports 2010;10(4):278–86.
- Nicholson PJ, Cullinan P, Taylor AJ, Burge PS, Boyle C. Evidence based guidelines for the prevention, identification, and management of occupational asthma. Occupational & Environmental Medicine 2005;62(5):290–9.
- Couzos S, Murray R. Aboriginal primary healthcare: an evidence-based approach, 3rd edn. Melbourne: Oxford University Press, 2008.