Heat stress impacts human health through cumulative exposure

Dr. Andreas Flouris, Director of the FAME Lab at the University of Thessaly and scientific collaborator with the World Health Organization, is warning about the severe health impacts of prolonged heat exposure. He emphasizes that the cumulative thermal load over a 24-hour period is a critical factor, rather than just peak daytime temperatures.

When nighttime temperatures remain high, the body is unable to achieve a thermal balance or recover its functions. To maintain internal temperature, the body increases blood flow to the skin and produces sweat, which strains the heart and leads to the loss of essential electrolytes, salts, and fluids. This lack of nocturnal cooling prevents the body from resetting, creating a cumulative burden that carries over to the next day.

Research involving 7.4 million sleep records from over 47,000 individuals across 68 countries indicates that when minimum external temperatures exceed 30°C, the likelihood of reduced sleep duration increases significantly. This cumulative heat stress can lead to cognitive impairment, accelerated biological aging, and increased mortality rates, particularly among the elderly.