In recent times we have witnessed a wave of scientific articles that try to take advantage of the recent development of the so-called 'epigenetic clocks' to try to establish the effect on the speed of aging of multiple factors. These epigenetic clocks are based on the observation that the 'marks' with which DNA is modified or which modify histones, proteins that are involved in the compaction and organization of the genome around which DNA is wound, what we call the 'epigenome', accumulate as we age. The significance of this increased epigenetic modification of the genome during aging is unknown. Whether this happens randomly or follows established patterns, or whether it has functional consequences, altering, for example, how the information encoded in the genome is expressed, or is something accidental with no involvement in the aging process is currently unknown. In fact, there is much debate as to whether these epigenetic clocks truly and accurately reflect biological aging, as many claim. The most skeptical assert that the results of these studies are biased by selecting the clock or computer analysis that best suits the researchers' expectations.

In this particular case, the study variable is 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 whether heat accelerates biological aging, a conclusion they reached. In favor of the study, the authors used several epigenetic clocks, determined the biological age of the population and then tried to study whether there was a correlation between the acceleration of aging and the number of days of extreme heat recorded for the areas in which these people lived in the six years prior to the study.

In the absence of a better understanding of what these mathematical measurements really reflect and to what extent they are really related to biological aging, all these results must be taken with caution, especially because they conform to expectations and are observations, that is, they are not susceptible to being tested by proposing experiments that really establish a causal connection between clocks and heat (in this case).