Simon Quilty knows that on a hot day in Alice Springs he is going to have a busier day than usual ahead of him at the local hospital - but the reason for that will go unrecorded.
© Provided by ABC HealthDoctors believe heat is responsible for thousands more deaths than records show. (ABC Open: Brendan Mounter)
"All Territorians know that if you go for a very long walk on a very hot day you might not come back, because we feel how heat affects the body in all sorts of ways," he said.
"But if you die of a heart attack on a very hot day, your death certificate will say that you died of a heart attack - it won't reflect the ways in which heat contributed to your condition."
For the past 8 years the doctor and ANU lecturer has worked in the Northern Territory in some of the hottest towns in Australia, including Alice Springs and Katherine.
Dr Quilty said there were many ways high temperatures could affect the body and lead to death that was not explicitly diagnosed as heat stroke.
"With every degree that it gets hotter, we know that more people will die," he said.
"For instance, you are much more likely to have a heart attack when the weather is really hot, and that's complex but it's because your body is working harder to stay cool. Your heart may need to pump harder to help your body cool itself. If you become dehydrated, your blood becomes slightly thicker.
"So all these things together may contribute to you having a slightly increased risk of having a heart attack."
He said infections, heart disease, kidney disease and pneumonia were worsened by heat.
"When the whether is really hot here in Alice Springs or Katherine, I would say that perhaps half the people that are admitted into hospital . . . have something that has been pushed over the edge by heat," he said.
"For instance, maybe they had an epileptic seizure and that person falls on the ground and burns themselves on bitumen that is 70 degrees Celsius, or perhaps someone has run out of electricity at their house, so they try to get to the shopping centre for relief but they don't quite make it and they collapse on the way."
A silent killer
Dr Quilty and researchers want death certificates to include, not just the physiological reason that people died, but also the weather on the day they died.
"As a doctor practising for almost a decade in some of the hottest places in Australia, it's very clear that people will come into hospital incredibly unwell and that the very hot weather has almost certainly contributed to their sickness," he said.
"But there's a problem: once someone arrives in hospital, they are in a climate controlled environment. As a doctor, I'm not thinking about what's happening outside.
"As a doctor you are less likely to make the connection and don't have a way of recording it. There is nowhere for that information on death certificates."
The research team found that out of the 1,717,224 deaths in Australia between 2006 and 2017, heat was listed as a cause of death on fewer than 1,000 death certificates.
But the analysis of deaths and temperature found that heat was likely to have contributed to at least 37,000 of the deaths, although that relationship went unrecorded.
"There needs to be a clear space on a death certificate to include ecological factors and we need to educate doctors about the relationship between environment and health," Dr Quilty said.
He said the group of researchers he was part of wanted temperature, air quality and humidity recorded so death databases could be more nuanced.
Preparing for climate change
Last year, 41 temperature records were broken in the Northern Territory, including 54 days of temperatures above 40 degrees in Katherine.
Australian National University's Dr Arnagretta Hunter is also part of the research team and said including climate data on death certificates would let policy makers and medical teams make better decisions.
"As the climate changes and we expect to see more and more hot temperatures, we need to understand what the magnitude of that health effect might be," she said.
"What's alarming is that this hasn't been studied in great detail . . . but we actually don't understand the magnitude of this relationship between heat and mortality.
"We have made an extraordinary amount of policy decisions to save lives from coronavirus but the magnitude of the potential health risk from climate change is so much greater."
Expert in environmental health from the University of Sydney, Professor Ying Zhang, said without the data, thorough research was almost impossible.
"It's a great initiative. I fully support it." she said.
"The most commonly discussed limitation in existing heat and health research is in the under-reporting of heat-related health outcomes. There is no data for how it relates to death [and] hospital admissions.
"This results in significant underestimations of the real impact of heat on health."