The combination of extreme heat and air pollution may significantly increase the risk of having a fatal heart attack, especially among older individuals, according to new research.
The study, published Monday in Circulation, looked at more than 202,000 heart attack deaths between 2015 and 2020 in China. It found that days with extreme heat, extreme cold or high levels of fine particle air pollution were significantly associated with the risk of a fatal heart attack.
“Extreme temperature events are becoming more frequent, longer and more intense, and their adverse health effects have drawn growing concern,” senior author Yuewei Liu, an associate professor of epidemiology at the School of Public Health at Sun Yat-sen University in China, said in a press release.
The researchers found that during a two-day heat wave, the likelihood of a fatal heart attack increased by 18 per cent when temperatures ranged between 28 C and 37 C. However, in a four-day heat wave, with temperatures ranging from 35 C to 43 C, the risk surged to 74 per cent.
The deaths were among older adults with an average age of 77.6 years; 52 per cent were older than age 80; and 52 per cent were male.
The researchers estimated up to 2.8 per cent of heart attack deaths may be attributed to the combination of extreme temperatures and high levels of fine particulate matter pollution.
“Another environmental issue worldwide is the presence of fine particulate matter in the air, which may interact with extreme temperatures to adversely affect cardiovascular health,” Liu said.
The risk of a fatal heart attack was found to be twice as high during four-day heat waves when the fine particulate pollution (PM 2.5) levels exceeded 37.5 micrograms per cubic meter. That is more than double what the World Health Organization recommends for a three to four-day duration, which is 15 micrograms per cubic meter.
Fine particulates, which can come in the form of dirt, dust or smoke, are less than 2.5 microns in size and are so small that you cannot see them without a microscope, according to Health Canada. They have the ability to penetrate deep into people’s lungs and bloodstream, sometimes leading to serious health effects, including stroke and heart disease.
Mixing extreme heat with pollution
Dr. Justin Ezekowitz, cardiologist and professor at the University of Alberta in Edmonton’s Department of Medicine, said what is unique about this study is that it pairs weather with pollution when it comes to heart health, adding this has never been studied at this scale.
But extreme weather temperatures’ effect on the heart has historically been shown to increase someone’s risk of cardiovascular issues.
“Anytime somebody is trying to adapt to a temperature change, for example, high heat or very cold, the blood vessels have to either tightly constrict or dilate, (and) the heart has to create more cardiac output, which is basically generating more pumping for the same amount of effort,” he said.
“And then there’s a whole bunch of other things that happen in terms of how we regulate our skin temperature. And so the way we regulate that is very difficult on the heart, especially if the heart and somebody are susceptible.”
When you add PM 2.5 particles to the mix, such as ones your find in wildfires, “they both are having an effect on the blood vessels and heart. And the question is, are they amplifying each other, which is what we think is happening,” Ezekowitz said.
The researchers of the study stated they were unsure how, exactly, the co-exposure was increasing the risk of heart attack deaths.
“It remains unknown if and how co-exposure to extreme temperatures and fine particulate pollution might interact to trigger a greater risk of death from heart attack, which is an acute response potentially brought on by an acute scenario and a great public health challenge due to its substantial disease burden worldwide,” Liu stated.
How to stay safe
The study comes as many countries continue to experience record-breaking heat waves.
Last week, the world had the hottest week on record and is now entering into “uncharted territory,” according to the World Meteorological Organization (WMO).
Because extreme weather mixed with pollution may be the new norm, Ezekowitz warned that this study may only be the ” tip of what might be happening” with heart health and extreme weather. This is because the study out of China only looked at fatal heart attacks. He believes that the numbers would be higher if non-fatal heart attacks were also considered.
Despite the risk, there are ways to stay safe, Ezekowitz noted.
“Prevention is always going to be a better way to go about things. So the simple things, such as if we know it’s going to be a hot day out, if we are going to be outside, exercising and doing things we want to do to do those in the mornings when it’s cooler,” he said.
“And try to avoid very congested or busy areas where there is known pollution to do things such as activities outdoors.”
This is especially important if somebody is vulnerable to the effects of heat and pollution, Ezekowitz added. For example, individuals who work outside in road construction or are stationed at outdoor ticket booths with no means of escaping the heat or pollution.
“It’s about taking preventative measures and staying very well hydrated, making sure that the effects of temperature aren’t getting to you,” Ezekowitz said. “And then also make sure you limit your exposure, with breaks from the heat. That can also be quite a useful technique.”
— with files from Global News’ Eric Stober