A study has analyzed how extreme heat influences the biological age of older populations, specifically in the United States. The study, published in Science Advances, included blood samples from over 3,600 adults with an average age of 68 collected between 2010 and 2016.
The team compared epigenetic aging trends with days of extreme heat in the participants' places of residence. The models showed that more days of heat or prolonged heat —over a range of one to six years— increased the biological age of the participants by more than two years.
According to Manuel Collado, a scientific researcher at CNB-CSIC in CiMUS at the University of Santiago de Compostela, as reported by SMC, he explains that "we are witnessing a wave of scientific articles that seek to take advantage of the recent development of the so-called 'epigenetic clocks' to establish the effect on the aging rate of multiple factors. These epigenetic clocks are based on the observation that the 'marks' that modify DNA or modify histones, proteins that are involved in the compaction and organization of the genome around which DNA wraps, what we call 'epigenome,' accumulate as we age."
"The significance of this increased epigenetic modification in the genome during aging is unknown," Collado adds. "Whether this happens randomly or occurs through established patterns, or if it has functional consequences, altering for example how the encoded information in the genome is expressed, or if it is accidental without involvement in the aging process is currently unknown. In fact, there is much debate as to whether these epigenetic clocks truly reflect biological aging, as many argue. The most skeptical claim that the results of these studies are biased by selecting the clock or the computer analysis that best fits the researchers' expectations."
In this particular case, says Manuel Collado, "the study variable is the exposure to an increasing number of days of extreme heat. In an attempt to relate these extreme phenomena to their impact on human health, the researchers applied various epigenetic clocks to determine if heat accelerates biological aging, a conclusion they reached. In support of the study, the authors used several epigenetic clocks, determined the population's biological age, and then tried to study if there was a correlation between the acceleration of aging and the number of days of extreme heat recorded for the areas where these people lived in the six years prior to the study."
In the absence of a better understanding of what these mathematical measures truly reflect and to what extent they are truly related to biological aging, "all these results must be taken with caution," Collado assures, "especially because they conform to expectations and are observations, meaning they are not amenable to testing by proposing experiments that truly establish a causal connection between clocks and heat (in this case)."