[LUM#23] To Live Long, Let's Stay Cool
While heat remains summer’s greatest asset, increasingly frequent heat waves are set to become a major public health challenge. To protect healthcare systems and better target prevention campaigns, scientists are analyzing the psychological factors that motivate people to adopt safe behaviors during extreme heat. Marlène Guillon, a researcher at the MRE laboratory.
In 2003, the heat wave that gripped Europe left tens of thousands dead in its wake (approximately 15,000 in France, according to Santé publique France), sparking the first awareness of the issues related to excess mortality during heat waves: “Most of the early warning and prevention systems we have today date back to that year,” notes Marlène Guillon, a researcher at Montpellier Research in Economics.
While “I’m talking about a time that people under 20 can’t possibly know, ” future generations could experience ten times as many days of heat waves by 2100 in a +4-degree scenario, according to Météo France “Even if the temperature rise is limited to 2 degrees, healthcare systems will be put under severe strain if they don’t prepare,” predicts the researcher, co-author of a study on the psychological factors that drive adaptive behaviors during heat waves (“What Drives Adaptive Behaviors During Heat Waves? A Systematic Review with a Meta-Analysis”, Climate Policy, 2024).
Perceived effectiveness
In a review of the international literature, Marlène Guillon and her colleague at the University of Bordeaux, Mathieu Bourret Soto, identified 26 heat-adaptation behaviors, which they then classified into three categories: physical strategies “such as adjusting one’s clothing, drinking more water, or taking more showers”; home-based strategies, namely, “using a fan or air conditioning, closing the shutters”; and finally, activity-based strategies “such as avoiding going outside during the hottest hours or rescheduling physical activities for cooler times of day.”
The factor that most influences the adoption of these behaviors is perceived effectiveness, particularly in high-income countries. According to the researchers
, the information provided in prevention campaigns should be clear and easy to understand, using very simple infographics. “We could use a clock to illustrate the types of behaviors to adopt throughout the day: when to close the shutters, when to reopen them, and, most importantly, what the benefits are. Pointing out that this can lower the indoor temperature by 5 or 6 degrees encourages people to adopt these simple behaviors.”
Awareness and Perception of the Threat
Another important factor is, of course, knowing what actions to take, as well as the perception of the threat—which depends first and foremost on the ability to recognize an exceptional heat wave. “It’s counterintuitive, but the correlation between behavior and perceived threat is weaker in countries where average temperatures are higher. This can likely be explained by acclimatization to the heat, which makes people less wary,” explains Marlène Guillon. It is worth noting, however, one of the limitations of this study: the lack of available studies in Africa and South America and a lack of standardization in measurements regarding risk perception.
Researchers also noted a lower perception of risk and individual vulnerability among men and an insufficient perception among older adults, who appear less inclined to adapt. Prevention campaigns should therefore target these groups more effectively. But again, “we lack data to supplement these findings, and we recommend studying populations that were underrepresented in our meta-analysis—such as children or low-income individuals—whose housing conditions leave them particularly vulnerable to heat,” emphasizes Marlène Guillon.
Study in the South of France
Marlène Guillon and Mathieu Bourret Soto also conducted a study in 2022 involving 1,515 people living in the south of France (“Prevalence and factors associated with the adoption of heat-adaptive behaviors among residents of a French southern region,” Journal of Environmental Psychology, 2026). They analyzed eight heat-adaptive behaviors: drinking more water; closing the shutters; postponing activities until cooler hours; taking more showers; avoiding the sun between noon and 4 p.m.; going to cooler places; and finally, avoiding dehydrating beverages such as alcohol or coffee. The researchers found that the first three behaviors listed were adopted significantly more often. Why? “Once again, it is the perception of effectiveness that determines the adoption of these behaviors, but so does social norms. If all your neighbors close their shutters, you’ll tend to follow their example; the same goes if you see your coworkers drinking water,” explains Marlène Guillon.
Underestimating the danger
Conversely, reducing one’s consumption of dehydrating beverages, taking showers, or going to cool places are not behaviors that are widely adopted. “We assume here that these barriers are perceived obstacles. Older adults, for example, may view the travel time required to reach a cool place as a risk. Instead, they are more likely to close their shutters and stay indoors between noon and 4 p.m. ”
Prevention campaigns must therefore be based on leveraging social norms, highlighting the effectiveness of adaptive behaviors, and also “emphasizing the seriousness of the effects of heat on health. Many people underestimate the danger and go out for a jog at noon; it is crucial to better inform them,” concludes the researcher.
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