Data update: Short-term health impacts of the 2019–20 Australian bushfires

The bushfire season

For comparability, data for this report were limited to a selected period, which varied slightly to accommodate leap years. For analyses related to admitted patient hospitalisations, emergency department presentations, and the Medical Benefits Schedule (MBS; all mental health items analysis only), this period was from 1 September to 1 March (for non-leap years: 2014–15, 2016–17, 2017–18 and 2018–19) and 1 September to 29 February (for leap years: 2015–16 and 2019–20). This period is referred to in reporting as the ‘bushfire season’.

Counts and rates were organised by week, grouped into 7-day periods beginning on 1 September for all years analysed. The comparison period for admitted patient hospitalisations and all Medicare-subsidised mental health services was the average of the previous 5 years (2014–15 to 2018–19). For emergency department presentations, the comparison period was the previous year (2018–19) for reasons of comparability, as the Emergency Department ICD-10-AM Principal Diagnosis Short List was implemented from 2018–19.

Strava Metro data were grouped by weeks, with Monday as the first day. The 2019–20 bushfire period for these purposes was from 2 September 2019 to 1 March 2020, with the previous year (3 September 2018 to 3 March 2019), used for comparison.

For MBS bushfire-specific mental health items, week groupings started after the introduction of the items and there was no comparison period.  

See Supplementary table S8 for a complete list of the weeks used in this report.

Crude rates (rates)

A crude rate, referred to as rate in this report, is defined as the number of events over a specified period (for example, a year or week) divided by the total population at risk of the event. It is then often multiplied by a set number to be expressed as a rate per standard unit of population (for example, number of hospitalisations per 100,000 persons) or as a percentage by multiplying the rate by 100.

The Australian Bureau of Statistics (ABS) Estimate Resident Population (ERP) for the end of the previous year’s reporting period was used as the denominators when calculating rates for admitted patient hospitalisations and emergency department presentations. For example, the population at 30 June 2018 was used to create rates for the 2018–19 period. Therefore, populations used in denominators reflect the population at the beginning of each reporting period. For bushfire-specific mental health Medicare Benefits Schedule (MBS) data, the ERP at the end of the quarter in which a given week occurred was used to calculate rates.

Statistical Area Level 4 (SA4)

Where possible, counts and rates have been reported by Statistical Area Level 4 (SA4), based on the ABS 2016 Australian Statistical Geography Standard (ASGS). A total of 88 SA4s are presented in this report, which excludes non-geographic codes and Other territories. A populated SA4 has around 100,000 to 300,000 people; metropolitan SA4s tend to have larger populations of around 300,000 to 500,000 people. In interpreting the results, note that where data are described at the state or territory level, the data include areas that were affected by fire or smoke as well as unaffected areas; this influences results at the state or territory level. Therefore, interpretation of data at the state or territory level is complemented by analysis at the SA4 regional level, to provide added detail in relation to short-term health effects of the 2019–20 bushfires. Many of the examples provided in this report are focused on jurisdictions most affected by bushfires and smoke: New South Wales, Victoria and the Australian Capital Territory.

National Hospital Morbidity Database

This section includes information relevant to interpretation of the National Hospital Morbidity Database (NHMD). Further information on the NHMD is available at <https://www.aihw.gov.au/reports-data/myhospitals/content/about-the-data> and a complete data quality statement is available online at <https://meteor.aihw.gov.au/content/index.phtml/itemld/181162>.

The NHMD is a compilation of episode-level records from admitted patient morbidity data collection systems in Australian hospitals.

The data supplied are based on the National Minimum Data Set (NMDS) for Admitted Patient Care and include demographic, administrative and length of stay data, as well as data on the diagnoses of the patients, the procedures they underwent in hospital and external causes of injury and poisoning.

The purpose of the NMDS for Admitted Patient Care is to collect information about care provided to admitted patients in Australian hospitals. The scope of the NMDS is episodes of care for admitted patients in all public and private acute and psychiatric hospitals, free-standing day hospital facilities, and alcohol and drug treatment centres in Australia. Hospitals operated by the Australian Defence Force, corrections authorities and in Australia’s off-shore territories are not in scope but some are included.

See the methodology section below for things to consider when interpreting these data.

Methodology

Data were grouped into 26, 7-day 'bushfire weeks' for each year of data, beginning on 1 September for all years and ending at 1 March for non-leap years and 29 February for leap years (See Supplementary table S8 for dates included in each week where comparisons were made). The dates reflect the date of admission of each episode of care.

Counts and crude rates based on principal diagnosis (see Table 1 below for groupings) were produced by bushfire week, state, and Statistical Local Area 4 (SA4).

Counts represent the number of hospitalisations for each reference week, reported by ICD-10-AM code aggregated into 1 of 11 condition groups (see coding details below).

Crude rate refers to number of hospitalisations per 100,000 persons. Rates for the 2019–20 bushfire season were calculated using the number of hospitalisations by bushfire week, state, and SA4 and condition group, divided by the estimated resident population at 30 June 2019 (see Crude rates (rates) above).

Crude rate for the previous 5-year average (per 100,000): Rate for the previous 5-year average was calculated as a weighted average of the crude rates for the years 2014–15 to 2018–19, to account for population change. Rates are expressed as hospitalisations per 100,000 persons.

Rate change (%) refers to the percentage change in the 2019–20 crude rate relative to the previous 5-year average crude rate.

The conditions (and associated ICD-10-AM codes) in Table 1 below were selected for inclusion based on existing literature on the health impacts of bushfires and bushfire smoke pollution.

Table 1: ICD-10-AM codes included in NHMD analyses

Condition	ICD-10-AM code(s)
Respiratory conditions	J00–J99
Asthma	J45–J46
Chronic obstructive pulmonary disease (COPD) with acute exacerbation	J44.1
Selected heart conditions	I10–I15, I20–I28, I30–I52
Cerebrovascular disease	I60–I69
Heart attack (Acute myocardial infarction)	I21
Mental health	F00–F99
Breathing abnormalities	R06.0–R06.8
Chest pain	R07.1, R07.3, R07.4
Dehydration	E86
Burns	T20–T31

ICD-10-AM codes for the above were included for all years of analyses as follows: 2014–15 (8th edition); 2015–16 and 2016–17 (9th edition); 2017–18 and 2018–19 (10th edition); 2019–20 (11th edition).

Records with missing sex and age were included in the analysis. The data exclude hospitalisations with a care type of hospital boarder, post humous organ procurement, and newborns with unqualified days only. Additionally, data exclude hospitalisations in Western Australia with a contracted patient status of 'Inter-hospital contracted patient to private sector hospital', to adjust for separations recorded on both sides of contractual care arrangements.

Analysis by geography

Geography is based on the patients’ state of usual residence, or area of usual residence—SA4, and not the jurisdiction or SA4 of the hospital at which the patient was admitted.

Reporting of results

In line with AIHW policy on reporting to manage confidentiality and reliability, as well as data management protocols for this dataset, where counts for diagnosis in a given week in a given jurisdiction or SA4 were less than 10, crude rates were not produced; where counts were 5 or lower for a particular disaggregation, both the counts and rates were suppressed. Secondary suppression was also applied throughout in the event that a suppressed cell could be identified from a higher level aggregation. Rates based on small numerators (particularly counts of less than 20) can be subject to volatility, and should be interpreted with caution.

Limitations and data considerations

The comparability of the coded diagnosis, intervention and external cause data can be affected by variations in the quality of the coding, and the numbers of diagnoses and/or interventions reported. Comparability can also be influenced by state-specific coding standards.

When considering numbers and rates in this report, it should be noted that variations in practices and policies may lead to variation among providers in the number of admissions for some conditions. Therefore, comparisons of hospitalisations across jurisdictions should be considered with caution Additionally, while care has been taken when choosing periods for comparison, changes in ICD-10-AM/ACHI classifications and the associated Australian Coding Standards may affect the comparability of the data over time.

Data based on the state or territory of residence should be interpreted with caution because of potential cross-border flows of patients.

National Non-admitted Patient Emergency Department Care Database

This section presents information on the emergency department data used in this report, and their limitations. The data quality statement and detailed data specifications for the National Non-admitted Patient Emergency Department Care Database (NNAPEDCD) is available online at <www.aihw.gov.au/about-our-data/our-data-collections/national-hospitals-data-collection>.

The data supplied by state and territory health authorities for the Non-admitted Patient Emergency Department Care (NAPEDC) National Minimum Data Set/National Best Endeavours Data Set (NMDS/NBEDS) were used by the AIHW to assemble the NNAPEDCD. The data cover waiting times and other characteristics of presentations to public hospital emergency departments.

The NNAPEDCD provides information on the care provided (including waiting times for care) for non-admitted patients registered for care in public hospital emergency departments that have:

• a purposely designed and equipped area with designated assessment, treatment, and resuscitation areas
• the ability to provide resuscitation, stabilisation, and initial management of all emergencies
• availability of medical staff in the hospital 24 hours a day
• designated emergency department nursing staff 24 hours per day 7 days per week, and a designated emergency nursing unit manager.

See the methodology section below for things to consider when interpreting these data.

Methodology

Data were grouped into 26, 7-day ' bushfire weeks' for each year of data, beginning on 1 September for all years and ending at 1 March for non-leap years and 29 February for leap years (See Supplementary table S8) for dates included in each week where comparisons were made. The dates reflect the date of presentation of each episode of care.

Counts and crude rates based on principal diagnosis (see Table 2 below for groupings) were produced by bushfire week, state, and Statistical Local Area 4 (SA4).

Counts represent the number of presentations for each reference week, reported by ICD-10-AM code aggregated into 1 of 11 condition groups (see coding details below).

Crude rate refers to number of presentations per 100,000 persons. Rates for the 2019–20 bushfire season were calculated using the number of presentations by bushfire week, state, and SA4 and condition group, divided by the estimated resident population at 30 June 2019 (see Crude rates (rates) above). Rates are expressed as presentations per 100,000 persons.

Rates for the 2018–19 bushfire season were calculated using the same methodology but with the estimated resident population at 30 June 2018 as the denominator.

Rate change (%) refers to the percentage change in the 2019–20 crude rate relative to the previous 2018–19 bushfire season crude rate.

The conditions (and associated ICD-10-AM codes) in Table 2 below were selected for inclusion based on existing literature on the health impacts of bushfires and bushfire smoke.

Table 2: ICD-10-AM codes included in NNAPEDCD analyses

Condition	ICD-10-AM code(s)
Respiratory conditions	J00–J99
Asthma	J45–J46
Chronic obstructive pulmonary disease (COPD) with acute exacerbation	J44.1
Selected heart conditions	I10–I15, I20–I28, I30–I52
Cerebrovascular disease	I60–I69
Heart attack (Acute myocardial infarction)	I21
Mental health	F00–F99
Breathing abnormalities	R06.0–R06.8
Chest pain	R07.1, R07.3, R07.4
Dehydration	E86
Burns	T20–T31

ICD-10-AM codes for the above were included for all years as follows: 2018–19 (10th edition short list); 2019–20 (11th edition short list)—comparisons with the 5 previous years were not made for data from the NNAPEDCD due to concerns about comparability of the data before the introduction of the short list.

Analysis by geography

Geography is based on the patients’ state of usual residence, or area of usual residence—SA4, and not the jurisdiction or SA4 of the emergency department at which the patient presented.

Reporting of results

In line with AIHW policy on reporting to manage confidentiality and reliability as well as data management protocols for this dataset, where counts for a diagnosis on a given week in a given jurisdiction or SA4 were less than 10, crude rates were not produced; where counts were 5 or lower for a particular disaggregation, both the counts and rates were suppressed. Secondary suppression was also applied throughout in the event that a suppressed cell could be identified from a higher level aggregation. Rates based on small numerators (particularly counts of less than 20) can be subject to volatility, and should be interpreted with caution.

Limitations and data considerations

A general concern with data from emergency departments is that diagnoses are not coded by qualified clinical coders, as they are for admitted patient care. Emergency department diagnoses data are coded at point of care by medical, nursing or clerical personnel.

Although the NNAPEDCD is a valuable source of information on emergency department care, the data have limitations. For example, sick or injured people who do not present to emergency departments are not included. Persons who present to an emergency department more than once in a reference year are counted on each occasion. Because the scope of the collection is limited to emergency departments that meet nationally agreed criteria, most of the data provided to the NNAPEDCD relate to emergency department care provided to people living in Major cities. The NNAPEDCD may not include emergency presentations to hospitals that have emergency departments that are not in scope for the Non-admitted Patient Emergency Department Care (NAPEDC) National Minimum Data Set (NMDS)/National Best Endeavours Data Set (NBEDS).

States and territories are primarily responsible for the quality of the data they provide. However, the AIHW undertakes extensive validations on receipt of data. Potential errors are queried with jurisdictions, and corrections and resubmissions may be made in response to these edit queries. The AIHW does not adjust data to account for possible data errors or missing values, except where stated.

Although there are national standards for data on non-admitted patient emergency department services, the way those services are defined and counted varies across states and territories, and over time. Therefore, comparisons of ED presentations across jurisdictions, and across time should be considered with caution.

For more detailed information on the data, see <https://www.aihw.gov.au/reports-data/myhospitals/content/about-the-data>.

Medicare Benefits Schedule (MBS) data

The MBS data presented relate to services provided on a fee-for-service basis for which MBS benefits were paid. The date is determined from the date the service was provided rather than the date the service was processed by Medicare.

Services Australia collects data on the activity of all persons making claims through the Medicare Benefits Scheme and provides this information to the Department of Health (Services Australia 2020). Information collected includes the type of service provided (MBS item number) and the benefit paid by Medicare for the service. The item numbers and benefits paid by Medicare are based on the Medicare benefits schedule book (Department of Health 2021). Services that are not included in the MBS are not included in the data.

See Supplementary tables S5 and S9 for a list of the MBS items used in the analyses. Further information on mental health-specific MBS items may be found at <https://www.aihw.gov.au/reports/mental-health-services/mental-health-services-in-australia/report-contents/medicare-subsidised-mental-health-specific-services/data-source-and-key-concepts#references>.

All Medicare-subsidised mental health conditions analysis

Notes on the analysis of all Medicare-subsidised mental health conditions are included below:

• MBS items included in the analysis are listed in Table S9 of the Supplementary tables.
• Crude rate (per 100,000) refers to number of services per 100,000 persons.
• For the analysis of bushfire-specific mental health items (Supplementary table S5), the population used to calculate the crude rate was the estimated resident population as at the end of the quarter in which the relevant week occurred, or the most recent available for services in 2021 (31 December 2020).
• For SA4 analysis (Supplementary table S6), the previous 5-year average crude rate was calculated as the weighted average crude rate over the 5-year period (that is total services / total population in that SA4).
• Comparison weeks were based on the same dates in the year over the previous 5 years, going back to 2014 (ensuring the period didn't run into 2020).
• The population used for the calculation of rates for the SA4 analysis was the estimated resident population at 30 June of the corresponding financial year in which the week occurred. For example, the population used for calculating comparison rates for the week 1 September to 7 September 2018 was the ERP at 30 June 2019.  
• An adjustment was made for the week containing the date of 29 February 2020—comparison weeks for all years except 2016 have an additional day added onto the end of the week to provide a 7 day time period.
• The last week of the period ends on March 1 for 2014–15, 2016–17, 2017–18 and 2018–19, and on February 29 for 2015–16, and 2019–20, to account for the leap year.
• Medicare services were allocated to SA4 based on the patient's enrolment postcode at the date of processing.
• Analysis of MBS mental health items was by date of service.
• Data for Other territories were excluded.

Further information on MBS data: see Medicare statistics—Services Australia.

Bushfire-specific mental health Medicare-subsidised service use

Notes on the analysis of bushfire-specific mental health MBS items are included below:

• On 10 January 2020, bushfire MBS mental health items were announced.
• From 17 January 2020, bushfire MBS mental health items were available to people whose mental health was adversely affected by a bushfire in the 2019–20 financial year. Therefore, counts and rates for the week beginning 12 January 2020 include 17–18 January 2020 only.
• MBS item numbers for claims by people whose mental health was affected by a bushfire in the 2019–20 financial year include services provided by:
  • GPs: 894, 896, 898, 2121, 2150, 2196, 91283, 91285, 91286, 91287, 91371, 91372, 91721, 91723, 91725,  91727, 91729, 91731
  • clinical psychologists: 91000, 91001, 91005, 91010, 91011, 91015
  • registered psychologists: 91100, 91101, 91105, 91110, 91111, 91115
  • social workers and occupational therapists: 91125, 91126, 91130, 91135, 91136, 91140, 91150, 91151, 91155, 91160, 91161, 91165.
• On 13 March 2020, new temporary COVID-19 MBS mental health telehealth items were introduced.
• From 20 April 2020, allied health service providers were no longer required to bulk-bill COVID-19 MBS mental health telehealth items. GPs and other medical professionals must bulk bill for Commonwealth concession card holders, children under 16 years old and patients who are more vulnerable to COVID-19.  
• On 2 August 2020, 10 additional Medicare psychological therapy sessions were made available to people subjected to further restrictions in areas affected by the second wave of the COVID-19 pandemic. This was available from 7 August 2020 to 31 March 2021.
• From 9 April 2020 to 30 June 2022, the 10 additional individual psychological therapy sessions were made available to all patients eligible under the existing MBS Better Access initiative.
• On 10 December 2020 eligibility requirements for the Better Access initiative were expanded to allow aged care residents to access up to 20 subsidised individual psychological services each calendar year.
• The reporting period for these items is 12 January 2020–6 March 2021.
• Medicare services are allocated to SA4 based on the patient's enrolment postcode at the date of processing.
• Analysis of MBS mental health items is by date of service.
• Counts of small numbers of services (less than 6) have not been presented for reasons of privacy and confidentiality.
• Crude rates are presented per 100,000 persons.
• Rates based on less than 10 services have not been reported for reasons of data reliability. Rates based on small numbers of services (particularly less than 20) should be interpreted with caution.

For further information on MBS data: see Medicare statistics—Services Australia.

Outdoor activity (Strava) data—Australian Capital Territory

This report presents information based on AIHW analysis of aggregated and de-identified data provided by Strava, through their Strava Metro platform. Strava is a platform that enables users to track, upload and share activities (trips) such as riding (bicycling), running, walking, or hiking, via a smartphone app or GPS-enabled hardware. Worldwide, Strava has over 85 million users and there are 40 million activities are uploaded to Strava each week. This data forms the basis for the Strava Metro platform, which allows partner organisations to analyse the data, usually for the purposes of improving active transport infrastructure. Strava Metro data includes activities from users that has been shared publicly and does not include activities shared privately or activities from people who have opted out of Strava Metro.

Strava granted the AIHW access to data for the Australian Capital Territory via the Strava Metro dashboard. In order to compare Strava user activity during the 2019–20 bushfire season with activity in the previous year, the proportional difference in total trips uploaded by Strava users for weeks in the period 2 September 2019–1 March 2020, relative to weeks in the previous period, 3 September 2018–3 March 2019 was calculated. It should be noted that activity tracking data may not give a comprehensive picture of the impact of bushfire smoke pollution on outdoor activity, as people can exercise without actively tracking and uploading their sessions. Additionally, during times of bushfire smoke, people might have performed more of their physical activity sessions indoors.

Additionally, the change (%) in the number of recorded trips doesn’t account for changes in the number of Strava users, or other seasonal effects such as air quality, temperature, or rainfall that may have occurred between the 2 periods, and should be considered with caution. It is also possible that some users may have left the Australian Capital Territory to avoid smoke pollution or have been affected by road closures during the height of the 2019–20 bushfire season.

Week groupings on the Strava Metro dashboard are based on weeks starting on a Monday rather than aligned according to date. Therefore, comparison weeks were aligned based on the week in the previous year which had the closest date to the week of interest.

References

Department of Health 2021. Medicare Benefits Schedule book. Viewed 21 August 2021.

Services Australia 2020. Education guide—Better Access to mental health care for eligible health professionals. Viewed 21 August 2021.