Gone are the summers of yore?

One record-breaking summer follows the other. As a popular saying goes, this may be the coolest summer of the rest of our lives. In Austria alone, multiple waves of 30+ degree Celsius days and long tropical nights are now part of the summer norm. The impact of heat on our cognition and physical health is a serious matter that cannot be overlooked.

Social psychologist Julia Reiter is currently investigating this issue, focusing on workers particularly affected by the heat, such as those working in construction or agriculture. These workers are exposed not only to high air temperatures but also to dangerous UV radiation. Sometimes, residue heat from industrial activities is added to the dangerous mix.

In these professions, it is often difficult to implement the usual recommended measures to alleviate heat stress, explains Reiter, a senior scientist at the Research Network on Health in Society at the University of Vienna: "It is often difficult to flexibly organise work or to shift it to the night or cooler seasons due to noise protection regulations or the traffic situation, for instance." But long-term consequences must also be considered: for example, construction workers without adequate protection may face a higher risk of skin cancer. "There are studies of field workers that show evidence of kidney damage, because at a certain point during heavy physical labour, you simply cannot drink enough to ensure the kidneys are adequately supplied."

However, heat affects us not only physically but also cognitively: it makes it harder to concentrate and causes tiredness and irritability. This leads to mistakes, increasing the likelihood of accidents at work. Conflicts in the workplace also become more frequent.

Enabling adaptation to heat

The feeling that one's ability to concentrate is impaired also leads to a constant, underlying fear of making mistakes, explains Reiter. This is because in some professions, mistakes can have serious consequences – for example, if medication is mixed up in a hospital: "It is an enormous psychological strain to be unable to perform as well as one would like over a prolonged period, despite one’s best efforts, whilst still bearing the same level of responsibility,” emphasises the expert.

Julia Reiter's research therefore also focuses on what employers can do to help improve the situation. "The primary aim, of course, is to reduce exposure to heat and sunlight, for example through shading and the provision of cooling rooms," she says. "But it's also about – and this is particularly challenging – changing work processes and social norms in the workplace, for example by allowing more breaks and adapting to the heat."

Errors caused by heat stress?

Can we effectively measure the effects of heat on mental performance? "The research on how heat affects concentration and attention is relatively mixed," says Claus Lamm, a cognitive researcher currently collaborating on a heat study: "Up to an air temperature of 45 degrees, the body – and therefore the brain too – is quite capable of adapting." Depending on how high the temperature is and how long the heat lasts, there are changes in concentration and cognitive ability in the single-digit percentage range: "One study showed that at 47 degrees, there is a decline of around six to seven percent. That means the system continues to function, but a little less effectively." That may sound like a small amount, but it is of course still significant – both on an individual level and for society as a whole. 

Certain groups are particularly affected

When trying to understand how heat stress increases the frequency of errors, the research landscape offers a mixed picture. For one, there are few meaningful studies on cognitive impairment at temperatures above 45 degrees: individual studies involving firefighters or military personnel, after all, cannot be extrapolated to the general population. However, one thing is consistently evident: the response to heat depends heavily on subjective perception, says Lamm: "Our subjective response to heat – that is, how stressful we perceive it to be – has a major influence on how negatively we actually react to it. Our brain and our perception have a massive impact on how we behave in rising heat, and to some extent also on our physiology." 

Nevertheless, certain groups are particularly vulnerable: babies, for example, are less able to dissipate heat than adults. Older people tend to drink less in general, which also impairs thermoregulation. Those who cannot avoid heat and direct sunlight at work are just as vulnerable as people with mental or physical illnesses, whose medication can have varying effects depending on the body's physiological state. Furthermore, some medications, such as antidepressants, have a negative impact on temperature regulation.

Alcohol is off limits

Extreme heat also places great demands on the bodies of the not-so-vulnerable. Under heat, heart rate, blood circulation, breathing and sweat production all increase. Physical activity should therefore be adjusted accordingly, says nutritionist and sports medicine specialist Daniel König: "As temperatures rise, you don't necessarily have to give up physical activity entirely. However, when temperatures exceed 35 degrees during the day or 25 degrees at night, our bodies are already operating at near capacity, and this means we need to refrain from physical activity." As a rule of thumb, König advises exercising at temperatures comfortable enough to air out one's home, seeking out open spaces such as nature reserves or parks, and adjusting the intensity of your training accordingly.

When it comes to diet, easily digestible meals should be chosen. Alcohol is off limits: "Alcoholic drinks can lead to a negative balance, as they increase excretion via the kidneys and dilate the skin’s blood vessels, which impairs the body's ability to cool down."

Heatwaves lasting longer and longer

Incidentally, the recommendation, often made in the past, to drink lukewarm drinks in hot weather is now outdated, says König: "Particularly in extreme temperatures, it can actually make sense to drink cold drinks, as this lowers the body's core temperature. What's more, many people simply prefer cold drinks." If this leads to people drinking more, the overall water balance remains in order.

In any case, with heatwaves starting earlier and lasting longer, it is not just vulnerable people but everyone who is forced to adapt their behaviour to stay healthy and productive: drink enough fluids, avoid heavy or excessive meals, shift activities to the early morning hours where possible, ventilate sensibly, and cool the body regularly by pouring cold water over your forearms or legs or taking a cold shower.