posts_gdocs: 1igCPBVxrbIRrDanvoWZ2RQIb8kXkKbKOBueDRgn5c7o
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1igCPBVxrbIRrDanvoWZ2RQIb8kXkKbKOBueDRgn5c7o | part-one-how-many-people-die-from-extreme-temperatures-and-how-could-this-change-in-the-future | article | { "toc": [ { "slug": "finding-the-goldilocks-spot-where-temperatures-are-most-comfortable-and-healthy", "text": "Finding the \u201cGoldilocks\u201d spot where temperatures are most comfortable and healthy", "title": "Finding the \u201cGoldilocks\u201d spot where temperatures are most comfortable and healthy", "supertitle": "", "isSubheading": false }, { "slug": "most-people-die-from-moderately-cold-conditions", "text": "Most people die from \u201cmoderately cold\u201d conditions", "title": "Most people die from \u201cmoderately cold\u201d conditions", "supertitle": "", "isSubheading": false }, { "slug": "how-many-people-die-from-sub-optimal-temperatures", "text": "How many people die from sub-optimal temperatures?", "title": "How many people die from sub-optimal temperatures?", "supertitle": "", "isSubheading": false }, { "slug": "cold-related-deaths-outnumber-heat-deaths-in-all-countries", "text": "Cold-related deaths outnumber heat deaths in all countries", "title": "Cold-related deaths outnumber heat deaths in all countries", "supertitle": "", "isSubheading": false } ], "body": [ { "type": "text", "value": [ { "text": "Think about someone dying from extreme temperatures. You probably pictured someone passing out from heat stroke or dying from hypothermia.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "But this is not how most people die from \u201cheat\u201d. They die from conditions such as cardiovascular or kidney disease, respiratory infections, or diabetes.", "spanType": "span-simple-text" }, { "url": "#note-1", "children": [ { "children": [ { "text": "1", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Almost no one has \u201cheat\u201d or \u201ccold\u201d written on their death certificate, but sub-optimal temperatures lead to a large number of premature deaths. As we\u2019ll see later, researchers estimate that it kills several million every year.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Older populations are usually most vulnerable to extreme temperatures. Most deaths occur in people older than 65. It\u2019s important to consider what \"death\" means here and how deaths from extreme temperatures might compare to other causes. Being too hot or cold can increase our risk of developing certain health conditions or worsen existing ones. It can thereby lead to an earlier death than would have occurred if the temperatures were \u201coptimal\u201d.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "How much time do hot or cold conditions take off someone\u2019s life? It\u2019s difficult to give precise estimates. One method that researchers often use is to look at excess death rates \u2014 which measure how many more people die in a given year compared to an \u201caverage\u201d year \u2014 in a particularly warm or cold year. Looking at patterns of excess deaths gives some indication of whether temperature-related deaths were \u201cbrought forward\u201d significantly or not.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "A study by Nirandeep Rehill and colleagues examined death patterns in the United Kingdom over 50 years.", "spanType": "span-simple-text" }, { "url": "#note-2", "children": [ { "children": [ { "text": "2", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" }, { "text": " It found that most cold-related deaths were among people who would not have died in the next 6 months. A later study looked at the impacts of high and low temperatures across a much larger sample of countries.", "spanType": "span-simple-text" }, { "url": "#note-3", "children": [ { "children": [ { "text": "3", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" }, { "text": " It found that most temperature-related deaths reduced lifespans for ", "spanType": "span-simple-text" }, { "children": [ { "text": "at least", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " one year. Most people died at least one year earlier, although there would be some that did lose less than this.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "In this article, I will examine how many people die from heat and cold each year and how researchers estimate these numbers. In a ", "spanType": "span-simple-text" }, { "url": "https://docs.google.com/document/d/1OSMBx0djXAo1Tb_3mvObyhvwOdsdcQ5kUuaNJVh5qK8/edit", "children": [ { "text": "follow-up article", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": ", I\u2019ll look at how these risks could change in the future due to climate change.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "A quick note on terminology: I will use the term \u201ctemperature-related deaths\u201d from this point forward to refer to the combination of deaths from heat", "spanType": "span-simple-text" }, { "children": [ { "text": " and ", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": "cold conditions. When I use the term \u201cheat\u201d, I mean warm or hot.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "text": [ { "text": "Finding the \u201cGoldilocks\u201d spot where temperatures are most comfortable and healthy", "spanType": "span-simple-text" } ], "type": "heading", "level": 2, "parseErrors": [] }, { "type": "text", "value": [ { "text": "To estimate temperature-related deaths, researchers estimate what is called the temperature-mortality relationship. This tells us how our risk of dying differs across the range of possible temperatures. To develop this relationship, scientists use real mortality records to understand \u201cexcess mortality\u201d \u2013 how many \u201cextra\u201d deaths occur above a given expected baseline \u2013 at different temperatures. Plot this increased risk against temperature, and you\u2019ll find a U-shaped curve.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Let\u2019s look at these \u201cmortality-temperature\u201d curves. I\u2019ve drawn a schematic below.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Your risk is lowest at the \u201coptimal temperature\u201d or \u201cminimum mortality temperature\u201d. This is the \u201cGoldilocks\u201d spot where the temperature is optimal: not too hot, not too cold, just right.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "On either side of this optimum, your health risks increase. The shape of this curve matters. In most locations, the rise in risk is relatively low at \u2018moderately cold\u2019 temperatures before rising sharply in extremely cold conditions. And they have a steep rise in risk at very warm temperatures.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "size": "wide", "type": "image", "filename": "heat-deaths-schematic.png", "hasOutline": false, "parseErrors": [] }, { "type": "text", "value": [ { "text": "Let\u2019s look at some real curves researchers use to estimate temperature-related deaths. Here, I\u2019ve taken some of the curves used in a ", "spanType": "span-simple-text" }, { "url": "https://www.nature.com/articles/s41467-024-45901-z", "children": [ { "text": "recent paper", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " published in ", "spanType": "span-simple-text" }, { "children": [ { "text": "Nature Communications", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " by Kai Chen and colleagues published in 2024.", "spanType": "span-simple-text" }, { "url": "#note-4", "children": [ { "children": [ { "text": "4", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" }, { "text": " These curves are very similar to those used in other leading studies in this field.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "I\u2019ve picked a selection of cities from across the world.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "What\u2019s immediately obvious is how different these curves are.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "First, they all have different optimal temperatures. It\u2019s lower in cities in colder regions of the world: around 18\u00b0C in Vancouver and London, compared to 25\u00b0C in Buenos Aires and Beijing.", "spanType": "span-simple-text" }, { "url": "#note-5", "children": [ { "children": [ { "text": "5", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Second, the shape of the curve varies a lot. In Paris, Vancouver, and Buenos Aires, mortality steepens at high temperatures. In Cape Town and Sao Paulo, it\u2019s at colder temperatures. In some cities \u2014 such as Tokyo or Austin \u2014 risks are low across the temperature range.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "size": "wide", "type": "image", "filename": "heat-mortality-curves.png", "hasOutline": false, "parseErrors": [] }, { "type": "text", "value": [ { "text": "These curves differ across places because people have acclimatized and adapted to the typical temperatures. This can be natural heat acclimatization \u2014 where our bodies physiologically adapt to tolerate hotter or colder temperatures \u2014 or technological adaptation, such as heating or air conditioning. People in Vancouver \u2014 and their homes \u2014 are well-adapted to very cold temperatures but are not adjusted to warm days.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Accordingly, mortality rates at very high temperatures can be low in Austin and Tokyo because most people have air conditioning. This is not true of Paris or London; it\u2019s still rare across many European countries.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "France was hit particularly badly when a large heatwave hit Europe in 2003. Around 15,000 ", "spanType": "span-simple-text" }, { "url": "https://www.metoffice.gov.uk/weather/learn-about/weather/case-studies/heatwave", "children": [ { "text": "people died", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": ". These temperatures \u2014 reaching as high as 40\u00b0C for more than a week in some cities \u2014 were an anomaly for the region in the early 2000s.", "spanType": "span-simple-text" }, { "url": "#note-6", "children": [ { "children": [ { "text": "6", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" }, { "text": " But they would not have been noteworthy and not particularly lethal in other parts of the world. The problem was that local populations who experienced milder summers did not know how to react to extreme heat. Even simple adaptation measures such as rehydration would have saved some people\u2019s lives.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "This is important: with the right resources, humans have the ability to adapt to different temperatures. That matters for how we cope with a warming world.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "text": [ { "text": "Most people die from \u201cmoderately cold\u201d conditions", "spanType": "span-simple-text" } ], "type": "heading", "level": 2, "parseErrors": [] }, { "type": "text", "value": [ { "text": "If you look at many of the \u201coptimal temperature\u201d curves above, you\u2019ll find that most of us spend most of the year a bit below the optimum. We most frequently experience temperatures a bit colder than is \u201cbest\u201d.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "This means most temperature-related deaths happen in \u201cmoderately cold\u201d conditions, not on extremely cold or hot days. It\u2019s not because the mortality risk in this zone is the highest, but the amount of time spent there is.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Again, this is not what most of us would think of as \u201ccold conditions\u201d. In the UK, this would include the increased risk of dying on days with a temperature of 10\u00b0C or 15\u00b0C. For us in Scotland, that\u2019s not cold: that\u2019s what we would consider a \u201cnice summer\u2019s day\u201d.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "This situation is not unique to the UK: moderate cold dominates temperature-related deaths across most of the world. The chart below comes ", "spanType": "span-simple-text" }, { "url": "https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(14)62114-0/fulltext", "children": [ { "text": "from a study", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " by Antonio Gasparrini and colleagues, published in ", "spanType": "span-simple-text" }, { "children": [ { "text": "The Lancet", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ".", "spanType": "span-simple-text" }, { "url": "#note-7", "children": [ { "children": [ { "text": "7", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" }, { "text": " It estimates the share of deaths in each country that can be attributed to temperature but is broken down by moderate and extreme cold and heat. You can see that \u201cmoderate cold\u201d dominates everywhere: from the UK and US to Thailand and Brazil.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "url": "https://ourworldindata.org/grapher/deaths-temperature-gasparrini", "type": "chart", "parseErrors": [] }, { "text": [ { "text": "How many people die from sub-optimal temperatures?", "spanType": "span-simple-text" } ], "type": "heading", "level": 2, "parseErrors": [] }, { "type": "text", "value": [ { "text": "There are now a range of studies looking at this question. All tend to fall within the range of several million. Most of these deaths occur in elderly populations, and as I mentioned earlier, the amount of life lost in most cases is around 6 months to a few years.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "A large ", "spanType": "span-simple-text" }, { "url": "https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(21)00081-4/fulltext", "children": [ { "text": "global study", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " by Qu Zaho and colleagues estimated temperature-related deaths from 2000 to 2019.", "spanType": "span-simple-text" }, { "url": "#note-8", "children": [ { "children": [ { "text": "8", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" }, { "text": " They estimated that 5 million people die prematurely from cold or heat-related deaths each year. That was equal to 9.4% of deaths from all causes. Almost one in ten deaths.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "An ", "spanType": "span-simple-text" }, { "url": "https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(14)62114-0/fulltext", "children": [ { "text": "earlier study", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " by Antonio Gasparrini and colleagues estimated that 7.7% of deaths in selected countries were attributed to temperature. This can\u2019t be directly compared to the 9.4% above, nor can it be used to estimate a global figure because not all countries were included. But it does show that a significant fraction of deaths across Australia, Brazil, Canada, China, Italy, Japan, South Korea, Spain, Sweden, Taiwan, Thailand, the UK, and the United States are linked to sub-optimal temperatures.", "spanType": "span-simple-text" }, { "url": "#note-9", "children": [ { "children": [ { "text": "9", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "The Global Burden of Disease (GBD) study ", "spanType": "span-simple-text" }, { "url": "https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)01700-1/fulltext", "children": [ { "text": "produces a lower", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " death toll: its latest report attributed 1.9 million deaths to non-optimal temperatures in 2021. Other studies ", "spanType": "span-simple-text" }, { "url": "https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(22)00179-9/fulltext", "children": [ { "text": "have suggested", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " that this is probably underestimated due to differences in methodology and the inclusion of data from a smaller subset of countries.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Some researchers ", "spanType": "span-simple-text" }, { "url": "https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(22)00073-0/fulltext", "children": [ { "text": "expect that", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " as many as 1.8 million deaths each year are attributed to ", "spanType": "span-simple-text" }, { "children": [ { "text": "short-term ", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": "temperature variability alone.", "spanType": "span-simple-text" }, { "url": "#note-10", "children": [ { "children": [ { "text": "10", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" }, { "text": " Large swings from cold to warm conditions, or vice versa, can put pressure on our organ systems and increase health risks.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "While estimates vary, depending on methodological differences, data quality, and assumptions about how humans respond to changes in temperature, the numbers are not small \u2014 they range from 1.7 to 5 million.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "To take account of the ", "spanType": "span-simple-text" }, { "children": [ { "text": "age", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " of people dying \u2014 and how much earlier they died \u2014 we would need to look at how many years of life had been lost. This multiplies the number of deaths by the number of years that their life was cut short. Unfortunately, only one of the studies above \u2014 the ", "spanType": "span-simple-text" }, { "url": "https://www.healthdata.org/research-analysis/gbd", "children": [ { "text": "Global Burden of Disease", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " \u2014 estimates the \u201cYears of Life Lost\u201d from sub-optimal temperatures. In estimates this was equal to 2% of the global total in 2021. That compares to 2.8% of deaths, which doesn\u2019t have any weighting for age.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "text": [ { "text": "Cold-related deaths outnumber heat deaths in all countries", "spanType": "span-simple-text" } ], "type": "heading", "level": 2, "parseErrors": [] }, { "type": "text", "value": [ { "text": "What\u2019s consistent in these studies is that cold-related deaths vastly outnumber those from heat.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "In the Global Burden of Disease study, cold-related deaths were around four times higher than heat-related ones.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "The study that estimates that 7.7% of deaths were attributed to temperature found that 7.3% were from cold temperatures; 0.4% were from heat.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "In the \u201c5 million death\u201d study, 9.4% of deaths were related to sub-optimal temperatures. 8.5% were cold-related, and 0.9% were heat-related. This skew was true across all regions.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "You can see these results in the chart below.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Globally, cold deaths are 9 times higher than heat-related ones. In no region is this ratio less than 3, and in many, it\u2019s over 10 times higher. Cold is more deadly than heat, even in the hottest parts of the world.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "url": "https://ourworldindata.org/grapher/temp-deaths-zhao", "type": "chart", "parseErrors": [] }, { "type": "text", "value": [ { "text": "There is a long list of other studies that provide similar results. A ", "spanType": "span-simple-text" }, { "url": "https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(23)00023-2/fulltext", "children": [ { "text": "study across", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " 854 cities in Europe found that cold-related deaths were around ten times higher than heat-related ones.", "spanType": "span-simple-text" }, { "url": "#note-11", "children": [ { "children": [ { "text": "11", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" }, { "text": " A detailed study across England and Wales found that cold-related deaths were two orders of magnitude higher.", "spanType": "span-simple-text" }, { "url": "#note-12", "children": [ { "children": [ { "text": "12", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" }, { "text": " The same is true for China.", "spanType": "span-simple-text" }, { "url": "#note-13", "children": [ { "children": [ { "text": "13", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" }, { "text": " And the United States.", "spanType": "span-simple-text" }, { "url": "#note-14", "children": [ { "children": [ { "text": "14", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Again, to be clear, most of these deaths come from ", "spanType": "span-simple-text" }, { "children": [ { "text": "moderately", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " cold conditions, not freezing temperatures. But it\u2019s a robust and consistent result within the scientific literature: today, more people die from cold than heat.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "This could change in the future as a result of climate change. In my ", "spanType": "span-simple-text" }, { "url": "https://docs.google.com/document/d/1OSMBx0djXAo1Tb_3mvObyhvwOdsdcQ5kUuaNJVh5qK8/edit", "children": [ { "text": "next article", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": ", I\u2019ll look at the increasing \u2014 and highly unequal \u2014 risk of heat deaths in a warming world.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "text": [ { "type": "text", "value": [ { "text": "Many thanks to Max Roser and Edouard Mathieu for their comments on this article and to Pierre Masselot for invaluable feedback on this research.", "spanType": "span-simple-text" } ], "parseErrors": [] } ], "type": "callout", "title": "Acknowledgements", "parseErrors": [] }, { "type": "horizontal-rule", "value": {}, "parseErrors": [] }, { "type": "text", "value": [ { "text": "This article is part of a series on extreme heat:", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "url": "https://docs.google.com/document/d/1igCPBVxrbIRrDanvoWZ2RQIb8kXkKbKOBueDRgn5c7o/edit", "type": "prominent-link", "parseErrors": [] }, { "url": "https://docs.google.com/document/d/1OSMBx0djXAo1Tb_3mvObyhvwOdsdcQ5kUuaNJVh5qK8/edit", "type": "prominent-link", "parseErrors": [] }, { "url": "https://docs.google.com/document/d/1hDUzWEqYFfr8p0vbVFJrsmfKvWC8qxm1bcLQ47-xvzM/edit", "type": "prominent-link", "parseErrors": [] }, { "url": "https://docs.google.com/document/d/164FakXXyQZ0e8ScHZELNSr5FFS33uuTBgMvoUzFJ6MQ/edit", "type": "prominent-link", "parseErrors": [] } ], "refs": { "errors": [], "definitions": { "2258ce0112f84c5947b7032b54180786f6ac2fcc": { "id": "2258ce0112f84c5947b7032b54180786f6ac2fcc", "index": 10, "content": [ { "type": "text", "value": [ { "text": "Masselot, P., Mistry, M., Vanoli, J., Schneider, R., Iungman, T., Garcia-Leon, D., ... & Aunan, K. 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The Lancet Regional Health\u2013Western Pacific.", "spanType": "span-simple-text" } ], "parseErrors": [] } ], "parseErrors": [] }, "f0579c7e4b299addc4335cc798aaa3589fca02d2": { "id": "f0579c7e4b299addc4335cc798aaa3589fca02d2", "index": 13, "content": [ { "type": "text", "value": [ { "text": "Lee, J., & Dessler, A. E. (2023). Future Temperature\u2010Related Deaths in the US: The Impact of Climate Change, Demographics, and Adaptation. GeoHealth.", "spanType": "span-simple-text" } ], "parseErrors": [] } ], "parseErrors": [] } } }, "type": "article", "title": "How many people die from extreme temperatures, and how this could change in the future: Part one", "authors": [ "Hannah Ritchie" ], "excerpt": "Cold deaths vastly outnumber heat-related ones, but mostly due to \u201cmoderate\u201d rather than extremely cold conditions.", "dateline": "July 1, 2024", "subtitle": "Cold deaths vastly outnumber heat-related ones, but mostly due to \u201cmoderate\u201d rather than extremely cold conditions.", "featured-image": "heat-mortality-featured-image.png" } |
1 | 2024-05-08 10:47:33 | 2024-07-01 08:20:00 | 2024-06-28 06:52:49 | listed | ALBJ4Lsw1rK0WRMujlQFCZIykqOqMnnyYdGUcz-ZOZNPNB3QewsJvF-Mjej6ROm-e3dYxdhV_7IB_yt1DRNfxg | Think about someone dying from extreme temperatures. You probably pictured someone passing out from heat stroke or dying from hypothermia. But this is not how most people die from “heat”. They die from conditions such as cardiovascular or kidney disease, respiratory infections, or diabetes.1 Almost no one has “heat” or “cold” written on their death certificate, but sub-optimal temperatures lead to a large number of premature deaths. As we’ll see later, researchers estimate that it kills several million every year. Older populations are usually most vulnerable to extreme temperatures. Most deaths occur in people older than 65. It’s important to consider what "death" means here and how deaths from extreme temperatures might compare to other causes. Being too hot or cold can increase our risk of developing certain health conditions or worsen existing ones. It can thereby lead to an earlier death than would have occurred if the temperatures were “optimal”. How much time do hot or cold conditions take off someone’s life? It’s difficult to give precise estimates. One method that researchers often use is to look at excess death rates — which measure how many more people die in a given year compared to an “average” year — in a particularly warm or cold year. Looking at patterns of excess deaths gives some indication of whether temperature-related deaths were “brought forward” significantly or not. A study by Nirandeep Rehill and colleagues examined death patterns in the United Kingdom over 50 years.2 It found that most cold-related deaths were among people who would not have died in the next 6 months. A later study looked at the impacts of high and low temperatures across a much larger sample of countries.3 It found that most temperature-related deaths reduced lifespans for _at least_ one year. Most people died at least one year earlier, although there would be some that did lose less than this. In this article, I will examine how many people die from heat and cold each year and how researchers estimate these numbers. In a [follow-up article](http://ourworldindata.org/climate-heat-deaths), I’ll look at how these risks could change in the future due to climate change. A quick note on terminology: I will use the term “temperature-related deaths” from this point forward to refer to the combination of deaths from heat_ and _cold conditions. When I use the term “heat”, I mean warm or hot. ## Finding the “Goldilocks” spot where temperatures are most comfortable and healthy To estimate temperature-related deaths, researchers estimate what is called the temperature-mortality relationship. This tells us how our risk of dying differs across the range of possible temperatures. To develop this relationship, scientists use real mortality records to understand “excess mortality” – how many “extra” deaths occur above a given expected baseline – at different temperatures. Plot this increased risk against temperature, and you’ll find a U-shaped curve. Let’s look at these “mortality-temperature” curves. I’ve drawn a schematic below. Your risk is lowest at the “optimal temperature” or “minimum mortality temperature”. This is the “Goldilocks” spot where the temperature is optimal: not too hot, not too cold, just right. On either side of this optimum, your health risks increase. The shape of this curve matters. In most locations, the rise in risk is relatively low at ‘moderately cold’ temperatures before rising sharply in extremely cold conditions. And they have a steep rise in risk at very warm temperatures. <Image filename="heat-deaths-schematic.png"/> Let’s look at some real curves researchers use to estimate temperature-related deaths. Here, I’ve taken some of the curves used in a [recent paper](https://www.nature.com/articles/s41467-024-45901-z) published in _Nature Communications_ by Kai Chen and colleagues published in 2024.4 These curves are very similar to those used in other leading studies in this field. I’ve picked a selection of cities from across the world. What’s immediately obvious is how different these curves are. First, they all have different optimal temperatures. It’s lower in cities in colder regions of the world: around 18°C in Vancouver and London, compared to 25°C in Buenos Aires and Beijing.5 Second, the shape of the curve varies a lot. In Paris, Vancouver, and Buenos Aires, mortality steepens at high temperatures. In Cape Town and Sao Paulo, it’s at colder temperatures. In some cities — such as Tokyo or Austin — risks are low across the temperature range. <Image filename="heat-mortality-curves.png"/> These curves differ across places because people have acclimatized and adapted to the typical temperatures. This can be natural heat acclimatization — where our bodies physiologically adapt to tolerate hotter or colder temperatures — or technological adaptation, such as heating or air conditioning. People in Vancouver — and their homes — are well-adapted to very cold temperatures but are not adjusted to warm days. Accordingly, mortality rates at very high temperatures can be low in Austin and Tokyo because most people have air conditioning. This is not true of Paris or London; it’s still rare across many European countries. France was hit particularly badly when a large heatwave hit Europe in 2003. Around 15,000 [people died](https://www.metoffice.gov.uk/weather/learn-about/weather/case-studies/heatwave). These temperatures — reaching as high as 40°C for more than a week in some cities — were an anomaly for the region in the early 2000s.6 But they would not have been noteworthy and not particularly lethal in other parts of the world. The problem was that local populations who experienced milder summers did not know how to react to extreme heat. Even simple adaptation measures such as rehydration would have saved some people’s lives. This is important: with the right resources, humans have the ability to adapt to different temperatures. That matters for how we cope with a warming world. ## Most people die from “moderately cold” conditions If you look at many of the “optimal temperature” curves above, you’ll find that most of us spend most of the year a bit below the optimum. We most frequently experience temperatures a bit colder than is “best”. This means most temperature-related deaths happen in “moderately cold” conditions, not on extremely cold or hot days. It’s not because the mortality risk in this zone is not the highest, but the amount of time spent there is. Again, this is not what most of us would think of as “cold conditions”. In the UK, this would include the increased risk of dying on days with a temperature of 10°C or 15°C. For us in Scotland, that’s not cold: that’s what we would consider a “nice summer’s day”. This situation is not unique to the UK: moderate cold dominates temperature-related deaths across most of the world. The chart below comes [from a study](https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(14)62114-0/fulltext) by Antonio Gasparrini and colleagues, published in _The Lancet_.7 It estimates the share of deaths in each country that can be attributed to temperature but is broken down by moderate and extreme cold and heat. You can see that “moderate cold” dominates everywhere: from the UK and US to Thailand and Brazil. <Chart url="https://ourworldindata.org/grapher/deaths-temperature-gasparrini"/> ## How many people die from sub-optimal temperatures? There are now a range of studies looking at this question. All tend to fall within the range of several million. Most of these deaths occur in elderly populations, and as I mentioned earlier, the years of life lost in most cases is around 6 months to a few years. A large [global study](https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(21)00081-4/fulltext) by Qu Zaho and colleagues estimated temperature-related deaths from 2000 to 2019.8 They estimated that 5 million people die prematurely from cold or heat-related deaths each year. That was equal to 9.4% of deaths from all causes. Almost one in ten deaths. An [earlier study](https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(14)62114-0/fulltext) by Antonio Gasparrini and colleagues estimated that 7.7% of deaths in selected countries were attributed to temperature. This can’t be directly compared to the 9.4% above, nor can it be used to estimate a global figure because not all countries were included. But it does show that a significant fraction of deaths across Australia, Brazil, Canada, China, Italy, Japan, South Korea, Spain, Sweden, Taiwan, Thailand, the UK, and the United States are linked to sub-optimal temperatures.9 The Global Burden of Disease (GBD) study [produces a lower](https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)01700-1/fulltext) death toll: its latest report attributed 1.9 million deaths to non-optimal temperatures in 2021. Other studies [have suggested](https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(22)00179-9/fulltext) that this is probably underestimated due to differences in methodology and the inclusion of data from a smaller subset of countries. Some researchers [expect that](https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(22)00073-0/fulltext) as many as 1.8 million deaths each year are attributed to _short-term _temperature variability alone.10 Large swings from cold to warm conditions, or vice versa, can put pressure on our organ systems and increase health risks. While estimates vary, depending on methodological differences, data quality, and assumptions about how humans respond to changes in temperature, the numbers are not small — they range from 1.7 to 5 million. To take account of the _age_ of people dying — and how much earlier they died — we would need to look at how many years of life had been lost. This multiplies the number of deaths but the number of years that their life was cut short. Unfortunately, only one of the studies above — the [Global Burden of Disease](https://www.healthdata.org/research-analysis/gbd) — estimates the “Years of Life Lost” from sub-optimal temperatures. In estimates this was equal to 2% of the global total in 2021. That compares to 2.8% of deaths, which doesn’t have any weighting for age. ## Cold-related deaths outnumber heat deaths in all countries What’s consistent in these studies is that cold-related deaths vastly outnumber those from heat. In the Global Burden of Disease study, cold-related deaths were around four times higher than heat-related ones. The study that estimates that 7.7% of deaths were attributed to temperature found that 7.3% were from cold temperatures; 0.4% were from heat. In the “5 million death” study, 9.4% of deaths were related to sub-optimal temperatures. 8.5% were cold-related, and 0.9% were heat-related. This skew was true across all regions. You can see these results in the chart below. Globally, cold deaths are 9 times higher than heat-related ones. In no region is this ratio less than 3, and in many, it’s over 10 times higher. Cold is more deadly than heat, even in the hottest parts of the world. <Chart url="https://ourworldindata.org/grapher/temp-deaths-zhao"/> There is a long list of other studies that provide similar results. A [study across](https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(23)00023-2/fulltext) 854 cities in Europe found that cold-related deaths were around ten times higher than heat-related ones.11 A detailed study across England and Wales found that cold-related deaths were two orders of magnitude higher.12 The same is true for China.13 And the United States.14 Again, to be clear, most of these deaths come from _moderately_ cold conditions, not freezing temperatures. But it’s a robust and consistent result within the scientific literature: today, more people die from cold than heat. This could change in the future as a result of climate change. In my [next article](https://ourworldindata.org/climate-heat-deaths), I’ll look at the increasing — and highly unequal — risk of heat deaths in a warming world. <Callout title="Acknowledgements"/> Zhao, Q., Zhang, Y., Zhang, W., Li, S., Chen, G., Wu, Y., ... & Guo, Y. (2017). Ambient temperature and emergency department visits: Time-series analysis in 12 Chinese cities. Environmental pollution, 224, 310-316. Lu, P., Zhao, Q., Xia, G., Xu, R., Hanna, L., Jiang, J., ... & Guo, Y. (2021). Temporal trends of the association between ambient temperature and cardiovascular mortality: a 17-year case-crossover study. Environmental Research Letters, 16(4), 045004. Chen, R., Yin, P., Wang, L., Liu, C., Niu, Y., Wang, W., ... & Zhou, M. (2018). Association between ambient temperature and mortality risk and burden: time series study in 272 main Chinese cities. Bmj, 363. Benmarhnia, T., Deguen, S., Kaufman, J. S., & Smargiassi, A. (2015). Vulnerability to heat-related mortality: A systematic review, meta-analysis, and meta-regression analysis. Epidemiology, 26(6), 781-793. Rehill, N., Armstrong, B., & Wilkinson, P. (2015). Clarifying life lost due to cold and heat: a new approach using annual time series. BMJ open, 5(4), e005640. Armstrong, B., Bell, M. L., de Sousa Zanotti Stagliorio Coelho, M., Leon Guo, Y. L., Guo, Y., Goodman, P., ... & Gasparrini, A. (2017). Longer-term impact of high and low temperature on mortality: an international study to clarify length of mortality displacement. Environmental Health Perspectives. Chen, K., De Schrijver, E., Sivaraj, S., Sera, F., Scovronick, N., Jiang, L., ... & Vicedo-Cabrera, A. M. (2024). Impact of population aging on future temperature-related mortality at different global warming levels. Nature Communications. Yin, Q., Wang, J., Ren, Z., Li, J., & Guo, Y. (2019). Mapping the increased minimum mortality temperatures in the context of global climate change. Nature Communications. Tobías, A., Hashizume, M., Honda, Y., Sera, F., Ng, C. F. S., Kim, Y., ... & Gasparrini, A. (2021). Geographical variations of the minimum mortality temperature at a global scale: a multicountry study. _Environmental Epidemiology_. Due to further warming, summers are now approaching those conditions in 2003, but after a more gradual increase over the course of the 2010s. Gasparrini, A., Guo, Y., Hashizume, M., Lavigne, E., Zanobetti, A., Schwartz, J., ... & Armstrong, B. (2015). Mortality risk attributable to high and low ambient temperature: a multicountry observational study. The Lancet. Zhao, Q., Guo, Y., Ye, T., Gasparrini, A., Tong, S., Overcenco, A., ... & Li, S. (2021). Global, regional, and national burden of mortality associated with non-optimal ambient temperatures from 2000 to 2019: a three-stage modelling study. The Lancet Planetary Health, 5(7), e415-e425. Gasparrini, A., Guo, Y., Hashizume, M., Lavigne, E., Zanobetti, A., Schwartz, J., ... & Armstrong, B. (2015). Mortality risk attributable to high and low ambient temperature: a multicountry observational study. The Lancet, 386(9991), 369-375. Wu, Y., Li, S., Zhao, Q., Wen, B., Gasparrini, A., Tong, S., ... & Guo, Y. (2022). Global, regional, and national burden of mortality associated with short-term temperature variability from 2000–19: a three-stage modelling study. The Lancet Planetary Health, 6(5), e410-e421. Masselot, P., Mistry, M., Vanoli, J., Schneider, R., Iungman, T., Garcia-Leon, D., ... & Aunan, K. (2023). Excess mortality attributed to heat and cold: a health impact assessment study in 854 cities in Europe. The Lancet Planetary Health, 7(4), e271-e281. Gasparrini, A., Masselot, P., Scortichini, M., Schneider, R., Mistry, M. N., Sera, F., ... & Vicedo-Cabrera, A. M. (2022). Small-area assessment of temperature-related mortality risks in England and Wales: a case time series analysis. The Lancet Planetary Health. Liu, J., Liu, T., Burkart, K. G., Wang, H., He, G., Hu, J., ... & Zhou, M. (2022). Mortality burden attributable to high and low ambient temperatures in China and its provinces: results from the Global Burden of Disease Study 2019. The Lancet Regional Health–Western Pacific. Lee, J., & Dessler, A. E. (2023). Future Temperature‐Related Deaths in the US: The Impact of Climate Change, Demographics, and Adaptation. GeoHealth. | How many people die from extreme temperatures, and how this could change in the future: Part one |