More women die in heatwaves, but biology 'isn't main cause'

More women die in heatwaves, but biology 'isn't main cause' August 1, 2026Observing recent heatwaves in Europe, one pattern has often been remarked on: More women appear to be dying than men. During Europe's then-record summer of 2022, a study found 56% more heat-related deaths among women than men, drawing on mortality data from 35 countries. Germany, which has just logged its deadliest heat season since 2016, with close to 9,800 heat-related deaths by mid-July, according to the Robert Koch Institute, is seeing the same pattern again this year. Are hormones making heatwaves more dangerous for women? Some of the recent coverage has leaned on the hormonal reading that women's bodies simply aren't equipped for heat. They sweat less, carry more body fat, and progesterone nudges core temperature up. But scientists who study the effect of heat on the human body say that's largely incorrect. "Overall, studies usually show only slightly more vulnerability to heat in women compared to men," saidAlexandra Schneider, an environmental epidemiologist and deputy director of the Institute of Epidemiology at Helmholtz Munich. "It's not really a very strong signal." The small differences that do exist are real: Women do have a lower sweat rate, less skin area relative to body size, and fat distribution that affects thermoregulation. Hormones play a role too, but unevenly across a lifetime. Schneider points to one group in particular: Women past menopause, when cardiovascular risk climbs. Older women with existing heart disease, she says, are probably at the highest risk of all. But even in those cases, she doesn't think biology is the main cause for the extra deaths during a heatwave. "The living conditions, the social environment where women live, makes probably even more of a risk than just the differences in hormone status." A research gap, not a biological difference Toby Mündel, a kinesiology professor at Brock University in Canada, who studies extreme human environments, says that the impact is "overstated," when asked whether there's a real biological basis for the claim that women are more likely to die in heatwaves. The factors that most determine how a person copes with a heatwave, Mündel says, are age, body size, fitness and habitual activity, and not biological sex. Sweating is one example. Even though women do sweat less, that doesn't make them more vulnerable, because they compensate in another way. "They send blood flow to the skin, vasodilation, much better than males do," Mündel says, meaning their blood vessels widen more efficiently, moving heat to the surface where it can escape. Pregnancy, which many assume must be dangerous, is another example. "As a woman progresses through pregnancy, she actually becomes better at handling heat," Mündel says. He draws a clear line between physiology and circumstance: There are good reasons not to have pregnant women doing heavy outdoor labor in extreme heat. But their bodies aren't the reason. Why does the data suggest otherwise? Partly, Mündel's argument is based on what gets measured. Studies often count hospital and emergency admissions, and women are far more likely than men to seek medical help. "That is not a physiological thing," he says. "Are they actually struggling, or have they just sought help earlier?" Underneath it all sits a research gap. "We have about a hundred times as much data and evidence on men. We have nearly zero on women," Mündel says. "It's like comparing cats and dogs." Numbers from Germany point in the same direction. The Robert Koch Institute attributes the higher female death toll to the fact that women make up a larger share of the oldest age groups. Its estimates also break down deaths per 100,000 people, and by that measure, the picture flips. In every older age band this summer, the male death rate is higher than the female one. In other words, more women are dying in heatwaves only because more very old women are alive. The real risk is exposure for women, not biology If the gap isn't physiological, where does it come from? Laurie Parsons, a researcher at Royal Holloway, University of London, studieshow heat stress moves through the global economy in construction, garment factories, farming, driving, street vending. Across the board, he says, women spend 30% to 50% more of their working time above heat-stress thresholds than men. In construction, when comparing men and women doing the same job, the figure rises to around 50%. The reasons, he says, are structural. Women often wear more clothing for the same job. Men are more confident asking for breaks. And where men's work is visibly strenuous, it's recognized as a heat risk and rewarded with rest. But women's work is steadier, less obviously punishing, and gets no such relief. Parsons compares it to the difference between a plane crash and asbestos exposure: One is a sudden, visible catastrophe, the other a slow, constant harm that's easy to miss. "Male heat stress tends to be this taller risk, where you get relatively visible moments of physical distress that can be managed," he says. "Female heat stress is constantly there, but much less visible, because it doesn't have those same obvious peaks in the working day." Then the shift ends, he says. Men rest, but women cook, clean and care for children. Heat also cuts into pay. Parsons says workers under heat stress are around 30% less productive in the garment sector, which he says is the easiest to quantify. In formal jobs, workers make up for it with longer hours during the hottest part of the day, feeding what he calls "a vicious cycle" of worsening health and falling output. The self-employed have no such buffer. For them, heat stress just means less income, which ripples the wider family over time. For Parsons, the starting premise is flawed. "Heat stress is not an atmospheric condition," he says. "It is a social condition, which happens within particular atmospheric circumstances." Edited by Ben Knight