During Victoria’s five day heatwave in 2009, metropolitan cardiac arrest cases increased by 2.8 times the average while there was a 62 per cent increase in total deaths from all causes.

This is evidence – produced by Victoria’s Health Department  – of the spike in deaths that arise in hot conditions and are informally known as ‘heat deaths’, according to president of the Australian Climate Health Alliance, Professor Liz Hanna.

“Heat deaths are deaths that would otherwise not be expected to occur and are as a result of exposure to more heat than the body can bear,” Dr Hanna told THORZT.

“When somebody gets too hot their normal physiological functions must kick in. If their capacity to cope with the heat is overwhelmed then their organs can fail.”

Heat deaths are generally under-reported by the medical system, according to Dr Hanna, who said this is particularly prevalent in rural areas.

“We don’t get sufficient data from rural Australia to crunch the numbers, but we know it gets very hot out there.”

“During heatwaves, there are lots of different diagnoses recorded as the cause of death. Failure of the cardiovascular system is very common – however it is the heat that has put the heart under stress,” she said.

Heat death risks are also increasing, according to Dr Hanna, who cited the Bureau of Meteorology’s (BOM) State of the Climate 2016 report.

The last three years have set an unprecedented run of record hot years for the globe since reliable records began in 1880 and the last 15 years are among the 16 warmest years on record, according to the report.

The BOM predicts Australian temperatures will continue increasing with more extremely hot days and fewer extremely cool days.

“As it gets hotter, more and more people will go beyond their capacity to withstand the heat,” Dr Hanna said, adding that this required better heat stress education and awareness to ensure people are prepared for extreme heat events. .” A  major problem in Australia, she added, was that people know Australia gets hot in summer, so they underestimate heat extremes, and underestimate their own risk.

“There is a big  push to reduce heat deaths, including advising people in the workplace, but it is still very important to get heat warnings out to those who are difficult to reach,” she said, citing those people as often being in rural areas or small workplaces, socially isolated, speaking another language or just busy.

“It is those who are uninformed and therefore unprepared who are most at risk. Heat warnings must get out in the media, and not just social media

In a bid to facilitate that, the BOM has launched their Heatwave Service, a set of maps showing colour-coded heatwave severity for the previous two three-day periods, and the next five three-day periods.

Heat Death Risks

While unpreparedness is a major factor, Dr Hanna said the elderly, very young and ill were also particularly at risk, along with anybody who is physically active in the heat.

“That can be anybody: construction workers, school children, even fit people who run marathons,” Dr Hanna said.

She added that heat tolerance – determined largely by previous exposure and cardiovascular fitness – is important and that everyone can improve, but acclimatisation erodes quickly and should not replace awareness and education.

“If you’ve got a big strong heart you can put up with a bit more, but those people tend to push themselves even  harder.”

She also said some people were naturally better at dealing with heat or building their heat tolerance.

“One of the really important things is people need to drink much more than they think. You should be hydrated enough that you need to go to the toilet every few hours.”

Heat Death Symptoms 

Symptoms usually start with fatigue and lethargy, a headache, fast heartrate, irritability or even confusion and cramps, according to Dr Hanna.

Later symptoms can include exacerbating confusion, excessive sweating which then stops, a weakening heartrate and very hot skin, or even cold and clammy skin.

“If your skin is cold and clammy you are in deep trouble – that basically means the cardiac system is getting close to shutting down.”

For more information, download THORZT’s free Heat Stress in the Workplace Guide.