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

While the evidence for an association between air pollution from bushfire smoke and heart, stroke and vascular conditions (also known as cardiovascular conditions, which includes events such as heart attack and stroke) is not as comprehensive as for respiratory conditions, several studies have found associations (see Australian bushfires 2019–20: exploring the short-term health impacts).

Analyses did not identify a consistent pattern in relation to impacts from bushfires and cardiovascular hospitalisations; however, there were examples of increases in hospitalisations for cardiovascular conditions coinciding with, or following, periods of poor air quality or fire activity. There were also some decreases in some jurisdictions and periods of the bushfire season, for particular conditions. The results suggest that further investigation is warranted regarding the extent to which these increases can be attributed to the effects of bushfire smoke pollution and whether there is a lag between exposure to air pollution and hospitalisation for cardiovascular conditions, as has been reported in the literature for some cardiovascular conditions (Walter et al. 2020). It should also be noted that other factors such as extreme heat (Loughnan et al. 2010), which often co-occurs with bushfire, may also lead to increases in hospitalisations.

Selected heart conditions

Nationally, there were increases in the hospitalisation rate for selected heart conditions (ICD-10-AM codes I10–I15, I20–I25, I26–I28 and I30–I52), coinciding with increased bushfire activity during the 2019–20 bushfire season, particularly in January and February 2020. The greatest increase in the hospitalisation rate was 8.8% in the week beginning 19 January 2020—31 per 100,000 persons (about 7,900 hospitalisations), compared with the previous 5-year average of 29 per 100,000 (an average of about 6,900 hospitalisations).

To explore national data and data for states and territories, see interactive data visualisations below (for data tables see Supplementary table S1).

Admitted patient hospitalisation rate, by jurisdiction, selected heart conditions (ICD-10-AM codes I10–I15, I20–I25, I26–I28 and I30–I52), weeks in 2019–20 bushfire season relative to previous 5-year average

At the state and territory level, examples of large increases in the hospitalisation rate for selected heart conditions coinciding with periods of significant fire activity or air pollution include:

• a 7.6% increase in the week beginning 19 January 2020 for New South Wales residents—30 per 100,000 persons (about 2,400 hospitalisations), compared with an average of 28 per 100,000 in the previous 5-year period (an average of about 2,200 hospitalisations)
• an 11% increase in the week beginning 5 January 2020 for Victorian residents—26 per 100,000 persons (about 1,700 hospitalisations), compared with an average of 24 per 100,000 in the previous 5-year period (an average of about 1,500 hospitalisations)
• a 52% increase in the week beginning 26 January 2020 for Australian Capital Territory residents—29 per 100,000 persons (about 125 hospitalisations), compared with an average of 19 per 100,000 (an average of 77 hospitalisations).

At the level of Statistical Area Level 4 (SA4), examples of large increases in the hospitalisation rate for selected heart conditions coinciding with periods of significant fire activity or air pollution include:

• a 63% increase in the week beginning 5 January 2020 for Far West and Orana residents—49 per 100,000 persons (57 hospitalisations), compared with an average of 30 per 100,000 in the previous 5-year period (an average of 35 hospitalisations). Much of the state experienced high levels of air pollution from bushfires during this week
• a 59% increase in the week beginning 12 January 2020 (the week when Victoria experienced its worst air quality) for Bendigo residents—50 per 100,000 persons (81 hospitalisations), compared with an average of 31 per 100,000 in the previous 5-year period (an average of 49 hospitalisations).

Further investigation is required to determine whether these increases are likely to be caused primarily by air pollution or other factors, particularly heat, and whether there are interactions between these factors.

For data by Statistical Area Level 4 (SA4), see Supplementary table S2.

Heart attack (acute myocardial infarction)

Among hospitalisations for heart conditions, hospitalisations for acute myocardial infarction (AMI; ICD-10-AM code I21), commonly known as heart attack, were also analysed separately as research has found specific associations with smoke pollution from bushfire (see Australian bushfires 2019–20: exploring the short-term health impacts). Note that hospitalisations for AMI are also included within selected heart conditions.

Nationally, there were increases in the hospitalisation rate for AMI coinciding with increased bushfire activity during the 2019–20 bushfire season. The greatest increase was 9.7% in the week beginning 19 January 2020—4.4 per 100,000 persons (about 1,100 hospitalisations), compared with the previous 5-year average of 4.0 per 100,000 (an average of 980 hospitalisations). The next greatest increase was 7.4% during the week beginning 5 January 2020.

To explore national data and data for states and territories, see interactive data visualisations below (for data tables see Supplementary table S1).

Admitted patient hospitalisation rate, by jurisdiction, AMI (ICD-10-AM code I21), weeks in 2019–20 bushfire season relative to previous 5-year average

At the state and territory level, examples of large increases in the hospitalisation rate for AMI coinciding with periods of significant fire activity or air pollution include:

• a 20% increase in the week beginning 5 January 2020 for Victorian residents—4.3 per 100,000 persons (about 280 hospitalisations), compared with an average of 3.6 per 100,000 in the previous 5-year period (an average of 220 hospitalisations)
• a 45% increase in the week beginning 5 January 2020 for Western Australian residents—5.4 per 100,000 persons (about 140 hospitalisations), compared with an average of 3.7 per 100,000 in the previous 5-year period (an average of 95 hospitalisations).

Numbers of hospitalisations for AMI at the level of Statistical Area Level 4 (SA4) were generally small and should be considered with caution. However, examples of large increases in the hospitalisation rate for AMI coinciding with periods of significant fire activity or air pollution include:

• a 96% increase in the week beginning 1 December 2019 for Central Coast residents—12 per 100,000 persons (42 hospitalisations), compared with an average of 6.2 per 100,000 in the previous 5-year period (an average of 21 hospitalisations). An increase of about 115% also occurred in the week beginning 8 December 2019. The maximum hourly PM2.5 values during these weeks at Wyong, on the Central Coast of New South Wales were 359 µg/m³ and 161 µg/m³ respectively
• a 90% increase in the week beginning 5 January 2020 for Perth – North West residents—6.5 per 100,000 persons (37 hospitalisations), compared with an average of 3.4 per 100,000 in the previous 5-year period (an average of 19 hospitalisations). A similar increase also occurred in Perth – North East during this week. During this time, an emergency warning was in place as fires burned to the north of Perth, threatening a number of communities (ABC News 2020).

For data by Statistical Area Level 4 (SA4), see Supplementary table S2.

Cerebrovascular conditions

Some evidence suggests that exposure to bushfire smoke may increase the incidence of cerebrovascular conditions (ICD-10-AM codes I60–I69), including stroke (Edwards et al. 2018), therefore, hospitalisations for cerebrovascular conditions were analysed. There were large variations in the rate of hospitalisations for cerebrovascular conditions in the previous 5 years, and it was not possible to identify a consistent pattern between air quality and hospitalisations for cerebrovascular conditions. However, there did appear to be some notable increases in the hospitalisations rate coinciding with bushfire activity during the 2019–20 bushfire season in some jurisdictions.

Nationally, the largest increase in the hospitalisation rate was 16% in the week beginning 17 November 2019—6.5 per 100,000 persons (1,600 hospitalisations), compared with the previous 5-year average of 5.6 per 100,000 (an average of about 1,400 hospitalisations). A similar increase was observed in the week beginning 10 November 2019.

To explore national data and data for states and territories, see interactive data visualisations below (for data tables see Supplementary table S1).

Admitted patient hospitalisation rate, by jurisdiction, cerebrovascular conditions (ICD-10-AM codes I60–I69), weeks in 2019–20 bushfire season relative to previous 5-year average

At the state and territory level, examples of large increases in hospitalisation rate for cerebrovascular conditions coinciding with periods of significant fire activity or air pollution include:

• an 8.8% increase in the week beginning 12 January 2020 for Victorian residents—4.7 per 100,000 persons (about 310 hospitalisations), compared with an average of 4.3 per 100,000 in the previous 5-year period (an average of 265 hospitalisations). However, there were also increases during times when air pollution was not particularly high (such as a 17% increase in Victoria in the week beginning 20 October 2019). This suggests that further analysis is needed to establish the extent to which increases in cerebrovascular hospitalisations can be attributed to the effects of bushfires (such as air pollution)
• a 34% increase in the week beginning 17 November 2019 for Queensland residents—8.4 per 100,000 persons (about 425 hospitalisations), compared with an average of 6.2 per 100,000 in the previous 5-year period (an average of about 305 hospitalisations). This coincided with a period of poor air quality in south-eastern Queensland around this time and the preceding days (ABC 2019; Arriagada et al. 2020; supplementary material).

Numbers of hospitalisations for cerebrovascular conditions at the level of Statistical Area Level 4 (SA4) were generally small and should be considered with caution. However, some notable examples of increases in the hospitalisation rate, coinciding with, or following periods of significant fire activity or air pollution include:

• an 85% increase in the week beginning 5 January 2020 for Newcastle and Lake Macquarie residents—12 per 100,000 persons (46 hospitalisations), compared with an average of 6.6 per 100,000 in the previous 5-year period (an average of 24 hospitalisations)
• an 83% increase in the week beginning 26 January 2020 for La Trobe – Gippsland residents—9.4 per 100,000 persons (27 hospitalisations), compared with an average of 5.1 per 100,000 in the previous 5-year period (an average of 14 hospitalisations).

For data by Statistical Area Level 4 (SA4), see Supplementary table S2.