Asthma in Australia 2008Header
Table of Contents | Chapter 1  2  3  4  5  6  7  8  | Appendix 1 2 | References |


5. Use of health services

| Introduction | 5.1 General practice encounters | 5.2 Hospitalisations and emergency department visits for asthma | 5.3 Invasive mechanical ventilation | 5.4 Health–care expenditure |

5.2 Hospitalisations and emergency department visits
| 5.2.1 Emergency department visits | 5.2.2 Hospitalisations | 5.2.3 Time trends in hospital use for asthma | 5.2.4 Seasonal variation | 5.2.5 Population subgroups | 5.2.6 Comorbidities in patients admitted to hospital with asthma | 5.2.7 Asthma as an additional diagnosis in people admitted to hospital with other conditions | Summary |

Key points

  • Children have higher rates of hospitalisation for asthma than adults.
  • There has been a reduction in the rate of hospital admissions for asthma between 1993–94 and 2006–07, which has occurred among both adults (–45%) and children (–42%).
  • Hospital admissions for asthma are higher in boys compared with girls, adult women compared with adult men, people from English-speaking backgrounds compared with those from a non-English-speaking background, adults living in remote areas compared with adults residing in major cities and people living in socioeconomically disadvantaged areas compared with those living in the least disadvantaged areas.
  • Peaks in hospital admissions for asthma vary by age, with rates highest in February and May among children and highest in the winter months among adults.
  • Respiratory infections are commonly listed as an associated diagnosis among people of all ages admitted to hospital for asthma.

5.2.1 Emergency department visits                     [back to top]

People with asthma may visit an emergency department (ED) when they experience an exacerbation or worsening of their disease. Since exacerbations may be a feature of severe or poorly controlled asthma, rates of ED visits for asthma are often considered to reflect the prevalence of severe or poorly controlled asthma in the community (Vollmer et al. 2002). The occurrence of ED visits for asthma may also be a useful indicator of the effects of interventions to improve disease control in patients with asthma (Bateman et al. 2004) and the effect of environmental exposures on asthma control (Forbes et al. 2007).

However, going to an ED is only one of a range of alternatives available for managing less severe flare-ups of asthma. Hence, variation in ED visits may, in part, be attributable to variation in access to general practitioner care (including after hours and home visit accessibility) and in the use of self-management plans for exacerbations. Also, the accessibility of the ED care itself may influence the likelihood that people with worsening of asthma will seek this care. Finally, it should be noted that not all ED visits for asthma are attributable to exacerbations of asthma. There is some evidence to show that people may use EDs as a source of routine primary care (Ford et al. 2001).

In this section we present the time trend in data obtained from the New South Wales Emergency Department Data Collection.

There were marked month-to-month fluctuations in the rate of ED visits for asthma, particularly among children under the age of 15 years (Figure 5.17). Of note, the lowest rate of ED visits for asthma consistently occurred in January when there was also the least difference between age groups. At other times of the year, the rate of visits to an ED for asthma was much higher among children aged 0–14 years than in all other age groups. Both the timing and the size of peaks in rates of ED visits varied with age (Figure 5.17). Among children under the age of 15 years, the peak ED visit rate was in late summer, with several very large peaks occurring, most notably in February 1999, 2001 and 2006. Peaks in ED attendance rates for asthma among children also occurred in May 2002, 2004, 2005 and 2007. Among people aged 65 years and over, and to a lesser extent those aged 35–64 years, the fluctuations in ED visit rates were less marked. Small peaks in ED visit rates for asthma among adults tended to occur in late autumn and winter.

In 2007, there were 22,942 ED visits for asthma in New South Wales. Among all people attending ED for asthma in New South Wales in 2007, 42% were admitted to hospital rather than being discharged home. The rate of admission to hospital for asthma from the ED was higher among children aged 0–14 years (48%) than among people aged 15 years and over (32%).

Figure 5.17: Emergency department visits for asthma per 100,000 population, by age and month, New South Wales, January 1999 to December 2007

5.2.2 Hospitalisations                     [back to top]

Hospitalisation for asthma is required when flare-ups or ‘attacks’ are life-threatening or when they cannot be managed at home.

Changes in the number of hospitalisations for asthma may be due to changes in the severity and prevalence of the disease in the community and the effectiveness of disease management. The use of hospital care for the management of exacerbations may also be influenced by the relative accessibility of hospital services and of alternative services such as general practitioners, especially after hours (Phelan et al. 1993, 2002). Changes in admission criteria and administrative policies also affect hospital usage data.

The risk of hospitalisation among people with asthma in Australia is low by comparison with other countries. An Australian study found that 3.8% of adults and 4.9% of children with asthma reported having been hospitalised for the condition in the past 12 months (Marks et al. 2007). This was lower than the rates reported in the global Asthma Insights and Reality surveys conducted in North America, Europe and Asia, where rates ranged from 7.0% for western Europe to 19.1% for central and eastern Europe (Rabe et al. 2004).

The data for this section are derived from the National Hospital Morbidity Database. In these data, the term ‘hospital separation’ refers to the formal process by which a hospital records the completion of treatment or care for an admitted patient. This includes completion due to discharge, death, transfer to another hospital or change in the type of care. Each separation represents one episode of hospitalisation (or admission). For more information on this database, see Appendix 1, Section A1.9.

There were 36,588 hospital separations with a principal diagnosis of asthma in 2006–07 in Australia. Asthma accounted for 0.48% of all hospital separations during that period.

5.2.3 Time trends in hospital use for asthma                     [back to top]

In 2006–07, the overall rate of hospital separations for asthma was 183.2 per 100,000 population, but the rate among children aged 0–14 years (533.6 per 100,000 population) was markedly higher than the rate among people aged 15 years and over (92.7 per 100,000 population).

Since 1993, there has been a substantial reduction in the rate of hospital separations for asthma in both children and adults (Figure 5.18; see also Appendix 2, Table A2.10). Between 1993–94 and 2006–07, hospitalisations for asthma decreased by 42% among those aged 0–14 years and by 45% among those aged 15 years and over.

Figure 5.18: Hospital separations for asthma per 100,000 population, by broad age group, 1993–94 to 2006–07

The decline in hospital admissions for asthma is not attributable to any parallel reduction in the prevalence of asthma over this period. It is possible that the decrease in hospitalisations for asthma is due to more effective long-term or preventative management of asthma or more effective out-of-hospital management of disease exacerbations. It is also possible that there has been a decrease in the severity of asthma over this period, due to environmental change. It is not possible to attribute the observed trend with any degree of certainty to any of these factors.

The average length of stay among people admitted to hospital for asthma has also gradually declined since 1998–99 (Figure 5.19). Among children hospitalised with asthma, the average length of stay decreased by 24% between 1998–99 and 2006–07. Among those aged 15 years and over, the average length of stay decreased by 32% during this time.

In 2006–07, the average length of stay for all persons admitted to hospital with asthma was 2.21 days. People aged 15 years and over tended to stay in hospital longer than children. The average length of stay for asthma in 2006–07 was 3.16 days among adults and 1.52 days among children.

Time trends in the rate of patient days for asthma since 1993–94 are shown in Appendix 2, Table A2.11.

Figure 5.19: Average length of stay for asthma, by broad age group, 1998–99 to 2006–07

5.2.4 Seasonal variation                     [back to top]

Among children, the peaks for hospitalisations occur in late summer and autumn (Figure 5.20). The reason for these seasonal peaks are not known, though they are likely to be related to a high prevalence of respiratory viral infections, particularly the common cold, around this time. Among adults, hospitalisation rates for asthma are highest in the winter months (Figure 5.20), which probably reflects the impact of the winter rise in respiratory tract infections, and early spring.

Figure 5.20: Seasonal variation in hospital separation rates for asthma, by age, children and adults, 2004

Large seasonal peaks in hospital admission rates for children have been observed in both the Northern and Southern Hemispheres in late summer. In New South Wales, it has been noted that these peaks coincide with the return to school after the holidays (Lincoln et al. 2006). It has been reported that peaks in hospital admissions for asthma are reached within 3.5 weeks of returning to school from the long summer holiday period, usually in February. Peaks in hospital admission rates have also been observed in May after shorter school holiday breaks (Lincoln et al. 2006). Studies conducted in the Northern Hemisphere have also observed increased asthma hospitalisation rates in children in early autumn, following school holidays (Johnston et al. 2005). The consistency of this pattern cannot be wholly explained by weather changes, the presence of allergens, airborne pollutants or viral infections. It has been suggested that the association between asthma admissions and returning to school may be related to the increase in social contacts at this time (Lincoln et al. 2006).

5.2.5 Population subgroups                     [back to top]

Age and sex

The highest rate of hospital separations for asthma was observed in children aged 0–4 years, particularly boys where the rate was 1,313 per 100,000 population in 2006–07.

Boys aged 0–14 years were more likely to be admitted to hospital for asthma than girls and, after the age of 15 years, females had a higher rate than males (Figure 5.21).

Figure 5.21: Hospital separations for asthma per 100,000 population, by age and sex, 2006–07

‘Patient days’ refers to the total number of full or partial days of stay for patients who were admitted to hospital for an episode of care and who underwent separation during the reporting period. A patient who is admitted and separated on the same day is allocated one patient day. The gender differences in the rate of patient days for asthma followed a similar pattern to hospital separations (data not shown).

These patterns are consistent with prevalence rates as well as the rate of asthma-related GP consultations.

Figure 5.22 further investigates hospital separation rates for asthma by age and sex in an effort to determine the exact age at which the rate declined in boys and increased in girls. From the age of 5–13 years, boys have higher rates of hospital separations for asthma than girls. Both the rates and the difference in rates between boys and girls gradually decline until age 13 years, when the rates are approximately equal. From the age of 14 years, the hospital separation rate for asthma continues to decline among boys and reaches a stable level at 16–18 years. Among girls, the rate starts to rise after 14 years and girls have higher rates of hospital separations for asthma than boys from this age.

Figure 5.22: Hospital separations for asthma per 100,000 population by 1-year age group and sex, ages 5–18 years, 2006–07

Compared with the general hospitalised population, those hospitalised for asthma are much younger. In 2006–07, more than half (58%) of all hospital separations for asthma were for children aged 0–14 years (Figure 5.23). In comparison, the proportion of all-cause hospital separations attributed to children was only 7%. In contrast, hospitalisations among people aged 65 years and over represented a much larger proportion of all-cause hospital separations than asthma separations (36% versus 9%, respectively).

Figure 5.23: Age distribution for hospital separations for asthma and all causes, 2006–07

The average length of stay for people hospitalised with asthma increased with age (Figure 5.24). The median length of stay (length of hospital stay for 50% of people) for asthma separations during 2006–07 was 1 day among 0–14 year olds compared to 4 days for people aged 65 years and over.

Figure 5.24: Relative frequency of length of stay for asthma, by broad age group, 2006–07

States amd territories

Among children, hospital separation rates for asthma in 2006–07 were lower than the national average in Queensland, Western Australia, Tasmania, the Australian Capital Territory and the Northern Territory and were higher than average in New South Wales and South Australia (Figure 5.25). Among adults, there was less variation in rates of hospital separations for asthma between the states and territories, although the rates in the Northern Territory and in South Australia were above the national average.

Figure 5.25: Hospital separations for asthma per 100,000 population among children and adults, by state and territory, 2006–07

Urban, rural and remote areas

Overall, the rate of hospital separations for asthma was 170.3 per 100,000 persons living in major cities and 226.4 per 100,000 persons living in very remote areas.

Among children aged 0–14 years, 72.3% of all hospital separations for asthma occurred in children residing in major cities. Children aged 0–14 years living in major cities had a higher hospital separation rate for asthma than those living in inner or outer regional areas (p < 0.0001) (Figure 5.26). In contrast, the hospital separation rate for asthma among people aged 15 years and over increased with increasing remoteness. The rate was significantly higher among those residing in very remote areas compared with those residing in major cities (p < 0.0001).

This pattern is consistent with the regional variation observed for all-cause hospital separations (AIHW 2008b).

Figure 5.26: Hospital separations for asthma per 100,000 population, by age and remoteness, 2006–07

Similar age trends were observed when examining the rate of patient days for asthma according to remoteness of residence (data not shown). For children aged 0–14 years, those living in major cities had a higher rate of patient days for asthma compared with those living in very remote areas. In contrast, there was a higher rate of patient days for asthma among adults living in very remote areas compared with adults living in major cities or regional areas (p < 0.0001). Among adults residing in major cities, the rate of patient days for asthma was 265.4 per 100,000 population while among adults residing in very remote areas of Australia, the rate of patient days was 461.9 per 100,000 population.

Among adults, there was also a significant association between the average length of stay for asthma and remoteness of residence (Figure 5.27). Adults residing in major cities had a longer length of stay for asthma (3.3 days) than adults who resided in very remote areas (2.5 days; p trend < 0.0001).

Figure 5.27: Average length of stay for asthma, by age and remoteness, 2006–07

Country of birth

Overall, the rate of hospital separations for asthma among those aged 5 years and over was higher among those from an English-speaking background (127.70 per 100,000 population) than among those from a non-English-speaking background (65.86 per 100,000 population) (p < 0.0001).

The disparity in hospitalisations for asthma according to country of birth diminished with age (Figure 5.28). Among those aged 65 years and over, there was no difference in the hospital separation rate for asthma according to country of birth (p = 0.4093).

Figure 5.28: Hospital separations for asthma per 100,000 population, by broad age group and country of birth, people aged 5 years and over, 2006–07

Similarly, the overall rate of hospital patient days for asthma among those aged 5 years and over was higher among people of English-speaking background (332.8 per 100,000 population) than those from a non-English speaking background (183.1 per 100,000 population) (p < 0.0001).

The age-related differences in rates of hospitalisations for asthma according to country of birth reflect the pattern of prevalence of the condition.

Socioeconomic disadvantage

Hospital separation rates for asthma increased with increasing socioeconomic disadvantage (p trend < 0.0001) (Figure 5.29). Overall, the rate of hospital admissions for asthma was significantly higher among those residing in the most disadvantaged localities (236 per 100,000 population) compared with those residing in least disadvantaged areas (140 per 100,000 population) (p < 0.0001). This trend was observed for all age groups.

Figure 5.29: Hospital separations for asthma per 100,000 population, by age and socioeconomic status, 2006–07

There was also a significant association between the level of socioeconomic disadvantage and the rate of patient days for asthma (data not shown). People residing in areas of relative socioeconomic disadvantage had a higher rate of hospital patient days for asthma than those residing in the least disadvantaged areas (p trend < 0.0001). Among those living in the most disadvantaged areas, the rate of hospital patient days for asthma was 522 days per 100,000 population, while among those living in the least disadvantaged areas, the rate of patient days for asthma was 297 days per 100,000 population.

5.2.6 Comorbidities in patients admitted to hospital with asthma                     [back to top]

The presence of one or more comorbid conditions in people with asthma is likely to compromise their quality of life and may complicate the management of the disease. In this section we investigate comorbidities by looking at the presence of additional diagnoses in people admitted to hospital with a principal diagnosis of asthma. It should be noted that conditions or disorders that do not affect the treatment received by the patient during their hospital stay are not included as additional diagnoses.

In 2005–06, 49% of patients admitted to hospital with a principal diagnosis of asthma had at least one comorbidity associated with their hospital stay. The proportion of patients hospitalised for asthma with at least one comorbidity increased with age from 45% among those aged 0–14 years to 69% among those aged 65 years and over (data not shown). More females (53%) than males (46%) hospitalised for their asthma had at least one comorbid condition.

As expected, the presence of comorbidity is associated with a prolonged length of hospital stay. The median length of stay for asthma was 2 days among those with at least one comorbidity compared with 1 day for those with no comorbidity (excluding same-day patients and those with a length of stay of more than 120 days).

Respiratory comorbidities

Of all hospitalisations due to asthma in 2005–06, 33.4% had an acute respiratory infection (ICD-10-AM codes J0–J22) as an additional diagnosis. In most of these cases, we can assume that the respiratory infection triggered the asthma exacerbation and subsequent hospitalisation. Respiratory infections occurred frequently as an associated diagnosis among children admitted to hospital with asthma. Just over one-third (34%) of all children aged 0–14 years who were hospitalised with asthma in 2005–06 had acute respiratory infections recorded as an additional diagnosis (Table 5.1). However, the occurrence of respiratory infections was also common in other age groups, with 32%, 28% and 28% of asthma admissions in people aged 15–34 years, 35–64 years and 65 years and over, respectively, being associated with such infections. As not all cases of respiratory infection are reported and some may have resolved before the hospital admission, it is likely that these data underestimate the role of respiratory infections as triggers for exacerbations leading to hospitalisation.

Other obstructive lung disease often coexists with a diagnosis of asthma, particularly among older people. Among people aged 65 years and over who were admitted to hospital with asthma, 5.2% had COPD or bronchiectasis as a comorbid condition.

Other comorbidities

This section examines the prevalence of several, specific comorbidities among people hospitalised with a principal diagnosis of asthma (Table 5.1). Among young adults aged 15–34 years admitted to hospital with asthma, mental and behavioural disorders were a common comorbidity, particularly among women (Table 5.1). The prevalence of diabetes as an additional diagnosis increased with age among adults from 2.0% to 11.9% to 18.3% among those aged 15–34 years, 35–64 years and 65 years and over, respectively. ‘Heart, stroke and vascular disease’ was listed as an additional diagnosis in 11.1% of asthma admissions among those aged 65 years and over.

Table 5.1: Comorbidities in people admitted to hospital with asthma, by age and sex, 2005–06 (per cent)

5.2.7 Asthma as an additional diagnosis in people admitted to hospital with other conditions                     [back to top]

Asthma was an additional diagnosis in 33,686 hospital separations in 2005–06, representing 0.5% of all hospital separations in that year where asthma was not the principal diagnosis (7,274,054 separations).

For patients admitted to hospital with an additional diagnosis of asthma in 2005–06, the most common principal diagnosis was influenza, pneumonia or other acute lower respiratory tract infection. Admissions with these lower respiratory tract infections accounted for 14% of separations where asthma was recorded as an additional diagnosis. For all patients admitted to hospital with a principal diagnosis of influenza, pneumonia or other acute lower respiratory tract infection in 2005–06, 40% had asthma recorded as an additional diagnosis. The likelihood of having asthma recorded as an additional diagnosis when the principal diagnosis was influenza, pneumonia or other acute lower respiratory tract infection decreased with age (96% of those aged 0–14 years compared with 17% of those aged 65 years and over), and was higher for females (48%) than males (32%).

Only just over 1% of all patients admitted to hospital with a principal diagnosis of COPD or bronchiectasis in 2005–06 had asthma recorded as an additional diagnosis. Younger people (5.3% of those aged 0–14 years) were more likely than older people (0.9% of those aged 65 years and over), and females (1.6%) were more likely than males (0.8%), to have asthma recorded as an additional diagnosis when COPD or bronchiectasis was the principal diagnosis.

The most common principal diagnoses associated with an additional diagnosis of asthma varied with age. The most common principal diagnosis among people aged 35–64 years was diseases of the digestive system while among people aged 65 years and over the most frequent principal diagnosis was circulatory disease. Presumably, these differences reflect the relative importance of these conditions as causes of hospitalisation in these age groups.

Summary                     [back to top]

Children have high rates of hospitalisation for asthma compared with adults, but adults tend to stay in hospital for asthma longer than children. There was an overall reduction in the rate of hospital admissions for asthma among children (42%) and among adults (45%) between 1993–94 and 2006–07. A reduction in the average length of stay for asthma admissions was also observed over the same period.

Children represent a far greater proportion of hospital admissions for asthma (58%) than total hospital admissions (7%).

Peaks in hospitalisation rates for asthma occur during winter among adults, while among children, the rate of hospitalisation for asthma is highest in February and May. A broadly similar seasonal pattern is observed in emergency department attendances.

Boys have higher rates of hospitalisation for asthma than girls. However, from age 14 years onwards, this trend is reversed and females have a higher rate of hospitalisation for asthma than males. These patterns are consistent with those observed for asthma prevalence and the rate of GP encounters for asthma.

Among adults, the rate of hospital separations for asthma increases with increasing remoteness. This trend is reversed among children, where the rate of hospital separations for asthma decreases with increasing remoteness.

Hospital separations for asthma are higher among those from an English-speaking background and those residing in disadvantaged localities

Respiratory infections and asthma are commonly associated causes of admission to hospital.

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