Asthma is a chronic inflammatory disorder of the lung's air passages that makes them narrow in response to various triggers, leading to episodes of shortness of breath and wheezing. There is no precise agreed definition of what constitutes asthma, since the symptoms of asthma can vary greatly in frequency and severity, ranging from intermittent mild symptoms to an incapacitating and life-threatening disorder.

Size of the problem

• In 1997, 27% of Australian children had current wheeze, and this is increasing by 1.4% per year.
• The prevalence of wheeze among adults is lower and appears to be stable.
• Up to 80% of adults with persistent asthma have abnormal lung function.
• Asthma contributed over 16,000 DALYs to the burden of disease in Victoria in 1996, or 2.6% of the total
• Mortality accounts for 14% of the asthma burden (approximately 200 deaths and 2,190 YLL p.a. in Victoria), with most of the burden due to disability
• Asthma is the sixth most common problem managed by GPs, the fourth most common reason for admission to hospital over all and is the most common reason for childhood admission to hospital
• Asthma is the most common cause of missing days at school and the cost to Australian companies through work days lost due to asthma is $110 million p.a.

Historical trends

• The prevalence of asthma in Australia has been doubling every fifteen years (self-reported asthma increasing from 8.5% in 1989-90 to 11.3% in 1995)
• Asthma deaths in Australia have fallen 28% since peaking in 1989, but the mortality rate is still twice that of England
• The prevalence of persistent asthma (wheezing episodes with abnormal airway function between episodes) in children has increased from 5% to 9% in the past 20 years. In adults, the prevalence is 5%-6%

International comparisons

• The prevalence of asthma in Australia is one of the highest in the world

Projections

• Since 1989, death rates for asthma have been declining and have recently approached the rates of the 1970s

Special populations

Asthma prevalence is higher among:

• Young people (aged under 25):
  Asthma is the leading cause of disease burden in Victorian children (20% of the total) and is more prevalent in young people (aged under 25) than older age groups

• Indigenous Australians:
  Asthma is a more commonly reported condition among Indigenous people than the Australian population as a whole and death rates due to asthma are higher

• Rural areas:
  • Asthma mortality shows significant regional variation with increased remoteness being associated with increased death rates (possibly contributed to by the larger Indigenous population, limited access to emergency and primary care, and higher exposure to a variety of chemicals and pesticides)

  • Hospitalisation rates for asthma are higher in rural than metropolitan areas (3.39 per 1000 pop. compared to 2.55 per 1000 pop. In 1997-98), although this gap seems to have narrowed over the previous four year period
    

• Socioeconomically disadvantaged groups:
  There is a significant trend for admission rates to increase linearly between the local areas of greatest socio-economic disadvantage (quintile 1 with over 3 admissions per 1000 pop.) to those areas which are the least disadvantaged (under 2 admissions per 1000 pop.)

Evidence-based interventions

• There is a lack of knowledge currently on how to prevent people from becoming asthmatic

• Control of environmental triggers (tobacco smoke, other air pollutants, workplaces with fine dusts or chemicals, house dust mites, pollens, moulds and animal dander) can reduce the frequency or severity of asthma attacks

• Asthma can be managed effectively through effective education, regular monitoring of symptoms or lung function, identification of trigger factors, co-ordinating self-management with written action plans and regular medical consultations

Asthma risk factors

1. Downstream (biomedical/physiological)
   • excess weigh
2. Midstream
• Behavioural: tobacco use; compliance with asthma management plan
• Demographic/socio-economic:
• low SES; Indigenous; CALD; Rural/remote residence
• Health services: Preventative services; access to effective and culturally appropriate primary health services
3. Upstream (physical/social environmental conditions; broader determinants of health)
   • Work environment
   • Government policie

References