Why women face greater health risks in extreme heat—what biology and science reveal

The studies are piling up. The numbers keep rolling in. And the question that’s quietly heating up global health conversations is this: Are women more vulnerable to heat than men?

It’s a concern that’s gained traction in recent years, especially as cities around the world grapple with heatwaves. Scientists are delving deep into this issue, and while there’s no single, clear-cut answer, the research is starting to paint a more complete picture.

The short version: The difference in heat tolerance between men and women is nuanced and it’s shaped by biology, physiology, and even social and hormonal factors. From how we sweat to how our bodies cool down, women may experience heat differently, and in some cases, less efficiently, than men.

The heat regulation divide: What science shows

Thermoregulation, which is our body’s way of maintaining a stable internal temperature, doesn’t work the same for everyone. In fact, men and women are built a little differently in this regard.

A study published in the Journal of Applied Physiology (2006) found that women generally start sweating at higher core temperatures than men and also produce less sweat overall. Since sweating is the body’s primary way of cooling down, this can be a disadvantage in hot or humid environments.

Translation: During a heatwave, women’s bodies might not be able to shed that excess warmth as quickly, which puts them at greater risk of suffering from heat stress.

Another study, this time from Experimental Physiology (2015), backed this up, finding that men have a higher rate of evaporative cooling during exercise in the heat. In simpler terms: Men’s sweat evaporates more easily, which means their bodies can cool down faster.

Size, shape and surface area: The hidden factors

It’s not just about sweat. Body size and composition also play an important role in how well someone copes with heat.

As research shows, women typically have a higher body fat percentage and a smaller body size compared to men. That means they have less surface area relative to body mass, which affects how quickly heat can escape from the body. These insights align with findings from a 2021 review in the Temperature journal, which noted that individuals with smaller body sizes, often including women, tend to experience greater heat strain. This happens usually, because their bodies retain more heat relative to the area available to release it.

So in hot environments, biology itself can make it harder for women to cool off — especially during physical activity.

The physiology puzzle

Soha Alhouby, Specialist in Obstetrics & Gynaecology at Medcare Medical Centre, Mirdif City, adds another layer to this complex picture. “Women have a lower rate of whole-body evaporative heat loss,” she explains. That means they’re simply not as efficient at releasing heat through sweating. This is partly because they have fewer sweat glands and tend to sweat less during activity.

She also notes that body fat, which are more present in women, acts like insulation, keeping the heat trapped inside. When combined with a smaller surface area, the body has fewer avenues to release that heat buildup. But it doesn’t stop there. Women, on an average, also have lower aerobic fitness levels than men, meaning their cardiovascular systems have to work harder in extreme temperatures. This added cardiovascular strain can further impact how the body manages heat stress.

Hormones in the heat: The role of menstrual cycles

As Singh and Yasir Shafi, Homeopathy Practitioner, Wellth explain, another factor that’s often overlooked, are hormones. Fluctuations in estrogen and progesterone levels during a woman’s menstrual cycle can cause her core body temperature to rise, particularly during the luteal phase, the second half of the cycle. This subtle shift can make women feel warmer and reduce their ability to tolerate additional heat.

Older women are at risk during heatwaves: What the science says

Historical data reveals a stark pattern. During the devastating 2003 European heatwave, which claimed over 70,000 lives, women, especially older women accounted for the majority of deaths. In France alone, 70 per cent of those who died were women, many of whom were over the age of 75, according to the European Journal of Public Health.

As the experts explain: As we age, our bodies naturally become less efficient at regulating temperature. Sweat gland function declines, skin blood flow decreases, and the sensation of thirst diminishes, all of which hinder the body’s ability to stay cool during heat exposure.”

Research suggests that these age-related changes may be even more pronounced in women. A study by Kenney and Munce (2003), published in the Journal of Applied Physiology, found that older adults have a reduced tolerance to heat due to impaired skin blood flow and decreased sweating. Among them, women showed a delayed onset of sweating and lower overall sweat rates, both of which are key to effective thermoregulation.

The challenges don’t end there. After menopause, women experience a sharp decline in estrogen, which is essential in maintaining healthy blood vessels and promoting skin circulation. With less estrogen, the body’s ability to cool down through vasodilation, the widening of blood vessels to release heat is diminished. Compounding this, older women are more likely to live with chronic conditions such as hypertension or osteoporosis, which can further compromise their heat tolerance. Many also take medications like diuretics, which increase fluid loss and heighten the risk of dehydration, making them even more susceptible to heat-related illnesses.

So, when you add it all up, from body composition to hormones to heat response, it’s clear that women’s bodies face unique challenges in extreme temperatures. And while everyone is vulnerable to heat-related illnesses during extreme conditions, the evidence shows that women may have to work a little harder to stay cool.