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Mortality & Morbidity: Asthma
SELF-REPORTED PREVALENCE OF ASTHMA AMONG CHILDREN AND ADULTS
Smoking and asthma
A recent report3 by the National Health and Medical Research Council (NHMRC) found that passive smoking is firmly linked, as a likely causal factor, to a range of health problems including lower respiratory tract disease and asthma in children. The NHMRC estimates that children exposed to environmental tobacco smoke are about 1.4 times as likely to suffer from asthma as children who are not exposed, and that around 8% of childhood asthma cases are attributable to passive smoking.
The 1995 NHS found that prevalence of asthma was higher (about 4 percentage points) among young children living in households with one or more smokers than in households with no smokers present. Among 10-14 year olds, however, prevalence of asthma was lower in households with smokers present. The Survey did not collect any information about whether children had ever been exposed to household smoking in the past, or whether they were currently exposed to smoking outside the home.
The 1995 NHS also found that asthma prevalence was higher among women who were either current smokers or ex-smokers than among those who had never smoked. For men, however, the relationship between asthma and smoking status appeared to be much weaker.
SMOKING AND SELF-REPORTED ASTHMA PREVALENCE RATES, 1995
(a) Aged under 15 years.
(b) Aged 18 years and over. Prevalence rates have been age standardised to the total population (aged 18 years and over) at 30 June 1995.
Source: 1995 National Health Survey: Asthma and other Respiratory Conditions, Australia (cat. no. 4373.0).
Treatment of asthma
Asthma can be controlled with preventive medications and strategies to reduce airway inflammation.1 In 1995, an estimated 1.1 million people (55% of all people with asthma) reported using medication for their asthma during the two weeks before interview. The proportion using medication increased steadily with age, from 49% of 0-14 year olds to 68% of those aged 65 years and over.
While children were less likely than other age groups to have used medication for their asthma, they were more likely to have seen a doctor. In 1995, 7% of 0-14 year olds with asthma had seen a doctor about it in the previous two weeks. Among adults, the proportion who consulted a doctor increased steadily with age, from 2% of 15-24 year olds to 6% of those aged 65 years and over.
Even with careful management, acute attacks of asthma cannot always be prevented and severe attacks may require treatment in hospital. The 1995 NHS estimated that 1% of children with asthma (6,400) had visited hospital casualty, emergency or outpatients units for asthma treatment during the two weeks before interview.
Hospital statistics compiled by the Australian Institute of Health and Welfare4 show that asthma is the most common medical condition for which children are admitted to hospital. For the year 1996-97, hospitals in Australia recorded asthma as the primary reason for 62,000 inpatient episodes, half of which related to children under 15 years of age. Asthma was the primary reason for 10% of all hospital inpatient episodes among 1-4 year olds and 5% among 5-14 year olds.
PEOPLE WHO TOOK RECENT(a) HEALTH-RELATED ACTIONS BECAUSE OF THEIR ASTHMA, 1995
(b) People may have taken more than one type of action. Therefore components may not add to totals.
(c) Includes people who took vitamins/minerals, used natural/herbal medicines, visited a hospital day clinic or were admitted to hospital as inpatients.
Source: Unpublished data, 1995 National Health Survey.
Reduced activity due to asthma
The 1995 NHS estimated that 1 in 26 children with asthma had taken one or more days off school (in the past two weeks) because of their asthma. Other than days away from school, 1 in 40 children with asthma had reduced their usual activities (e.g. sport, exercise) or stayed in bed for one or more days during the previous two weeks because of their asthma.
On the whole, asthma appeared to cause less disruption to the usual activities of adults than of children. For example, fewer than 1% of 25-64 year olds with asthma had taken a day off work in the past two weeks because of their asthma. With the exception of older people (aged 65 years and over), adults were also less likely than children to have had other days of reduced activity (i.e. other than days away from work or school) because of their asthma.
Deaths due to asthma
The risk of dying from asthma is relatively low. In 1997, asthma was the underlying cause of 715 deaths which represented 5% of deaths from respiratory diseases and less than 1% of all deaths in Australia. Asthma was recorded as a contributing cause in a further 1,157 deaths. As for most other causes of death, the rate of asthma deaths increases with age. In 1997, age-specific death rates from asthma ranged from less than 1 death per 100,000 of the population aged under 35 years, to just over 22 deaths per 100,000 of the population aged 65 years and over.
Age-standardised death rates from asthma (as the underlying cause of death) increased during the 1980s, peaking in 1989, but have since declined to below the 1982 rates for both males and females. Several researchers5,6,7 have found evidence to suggest that some of the increase in asthma death rates during the 1980s may have been due to diagnostic transfer, resulting in overstatement of asthma deaths, particularly among older people. Diagnostic transfer refers to a tendency to diagnose one condition rather than another owing to similarities in symptoms and changing recognition of diseases.
1 Jenkins, C.R. and Woolcock, A.J. 1997, ‘Asthma in adults’, Medical Journal of Australia, vol. 167, pp. 160-165.
2 Sporik, R., Holgate, S., Platt-Mills, T., Cogswell, J. 1990, ‘Exposure to house dust mite allergen (Der p1) and the development of asthma in childhood. A prospective study’, New England Journal of Medicine, vol. 323, pp. 502-507
3 National Health and Medical Research Council 1997, The health effects of passive smoking, A scientific information paper, AGPS, Canberra.
4 Australian Institute of Health and Welfare 1998, Australian Hospital Statistics 1996-97, AIHW, Canberra.
5 Jenkins, M.A., Rubinfeld, A., Robertson, C.F., Bowes, G. 1992, ‘Accuracy of asthma death statistics in Australia’, Australian Journal of Public Health, vol. 16, no. 4, pp. 427-429.
6 Campbell, D.A., McLennan, G., Coates, J.R., Frith, P.A., Gluyas, P.A., Latimer, K.M., Martin, A.J., Roder, D.M., Ruffin, R.E., Yellowlees, P.M. 1992, ‘Accuracy of asthma statistics from death certificates in South Australia’, Medical Journal of Australia, vol. 156, pp. 860-863.
7 National Health and Medical Research Council 1988, Asthma in Australia; Strategies for reducing morbidity and mortality, Report of the NHMRC Working Party on Asthma Associated Deaths, Canberra.