Submitted by: David Boettiger, Hunter New England Local Health District

Over summer Hunter Local Health District trialled an innovative community-driven system for monitoring heat-related illness in Australia.

Heatwaves in Australia are becoming hotter, longer, and more frequent.¹ They are responsible for more deaths than all other natural disasters combined,² and this gap is expected to widen with climate change and the increasing density of urban heat islands in our cities.³ Urban heat islands are areas that experience warmer temperatures than surrounding rural areas due to the heat generated by human activity and urban surfaces such as roads, paths and roofing. 

Nationally, there are 2,300 excess deaths attributable to heatwaves each year, equating to an annual cost of $AU6.8 billion.⁴ The total health costs are likely to be much greater as heatwaves are also associated with an increase in hospitalisations,⁵ emergency department visits,⁶ ambulance callouts,⁷ mental health episodes,⁸ and violent crime.⁹

However, the community health impact of heatwaves, including events that do not lead to medical care but still reduce wellbeing, are not well understood.

Hunter New England Local Health District (HNELHD) manage FluTracking Australia – a national surveillance system for monitoring respiratory infections on a community-level.¹⁰ FluTracking currently collects data from >50,000 volunteers across Australia who complete a weekly online survey describing symptoms of respiratory infection.

HNELHD leveraged FluTracking to test the feasibility of a community-driven system for monitoring heat-related illness in Australia. FluTracking participants in Sydney and Melbourne were invited to participate. Those who agreed were sent a weekly ‘HeatTracking’ survey over nine weeks of the 2024/2025 summer to indicate whether they had experienced any heat-related symptoms.

Heat-related symptoms included extreme thirst, dizziness, fainting, feeling too hot to sleep, feeling confused, cramping, lack of co-ordination, and a racing heartbeat.

There were 1,735 participants. Among these, 94% completed more than five weekly surveys, and 68% completed all nine weekly surveys. Heat-related symptoms were reported by 12-21% of participants each week.

After adjustment for temperature differences in the study locations, the main risk factors identified for heat-related illness included being older, being female, living in rental accommodation, frequently feeling hot due to work or exercise, and having a recent history of heat-related symptoms. Participants in Western Sydney had 30% greater risk of sleep difficulty than those in South-Eastern Sydney. This could be associated with the higher density of urban heat islands in Western Sydney compared with coastal parts of the city.

In those who reported heat-related illness, management of symptoms relied mostly on drinking fluids, using air-conditioning, and using a fan. Each week, 7-14% of those with heat-related symptoms needed time off normal duties and 1-3% needed medical care.

Overall satisfaction with HeatTracking was high among participants with 93% saying they would participate again.

Given these findings, HeatTracking appears to be a feasible approach to monitoring heat-related illness in Australian communities and could help inform local, state and national policies aiming to reduce the health impacts of climate change.

The full results of the HeatTracking study will be published soon.

References

1.     Trancoso R, et al. Heatwaves intensification in Australia: A consistent trajectory across past, present and future. The Science of the total environment 2020; 742: 140521.

2.     Coats L, et al. Exploring 167 years of vulnerability: An examination of extreme heat events in Australia 1844–2010. Environmental Science and Policy 2014; 42: 33-44.

3.     Chapman S, et al. The impact of climate change and urban growth on urban climate and heat stress in a subtropical city. International Journal of Climatology; 39(6): 3013-30.

4.     Beggs PJ, et al. The 2021 report of the MJA-Lancet Countdown on health and climate change: Australia increasingly out on a limb. The Medical journal of Australia 2021; 215(9): 390-2 e22.

5.     Xu Z, et al. Heatwave and infants' hospital admissions under different heatwave definitions. Environmental pollution 2017; 229: 525-30.

6.     Wondmagegn BY, et al. Impact of heatwave intensity using excess heat factor on emergency department presentations and related healthcare costs in Adelaide, South Australia. Sci Total Environ 2021; 781: 146815.

7.     Patel D, et al. Joint effects of heatwaves and air quality on ambulance services for vulnerable populations in Perth, western Australia. Environmental pollution 2019; 252(Pt A): 532-42.

8.     Hansen A, et al. The effect of heat waves on mental health in a temperate Australian city. Environ Health Perspect 2008; 116(10): 1369-75.

9.     Mahendran R, et al. Interpersonal violence associated with hot weather. Lancet Planet Health 2021; 5(9): e571-e2.

10.   Hunter New England Local Health District. FluTracking Australia New Zealand.  https://info.flutracking.net/ (accessed 30 Aug 2024)