In the fields of gerontology and anti-aging medicine, there is a commonly used distinction between biological and chronological age. Recent developments in epigenetics suggest that our epigenome—the chemical changes that happen above our DNA sequence—might be the key to understanding and calculating human biological aging. The distinction between biological and chronological age could have significant implications for how we should understand our legal age. Currently chronological age is used as a proxy for how well people function. But the results from epigenetics research imply that it may soon be possible to calculate a person’s biological age accurately. When that happens, shouldn’t our legal age be based on our biological rather than chronological age since biological age is a better indication on how able and well-functioning we actually are?
Dutchman Emile Ratelband (age 69 at the time) recently made headlines by wanting to change his birth date to 20 years later than the date he was born.  Ratelband claimed he has the body of a 50-year-old man and that he identifies as being younger than he currently is. Therefore, he claimed, he should be entitled to change his official age. The Dutch court rejected Ratelband’s appeal and many think he was not serious in his request in the first place.  However, there are people, for example, transhumanists, who think we should strive to stop biological aging and pursue eternal youth.  Since compared to chronological age biological age indicates more accurately what matters, such as functioning ability, should legal age change be allowed, if our aging process could be significantly decelerated or our biological age accurately measured?
In the fields of gerontology and anti-aging medicine, there is a commonly used distinction between biological and chronological age, which can be used as a base for claims of legal age change. While chronological age refers to the actual amount of time a person has existed, biological age refers to epigenetic alteration and DNA methylation which express on how able and functioning she is and whether she has diseases related to old age. Whereas chronological age increases at the same rate for everyone, biological age does not.  How fast our cells deteriorate depends on various factors: our genes and our lifestyle choices such as eating and exercising habits.  Recent developments in epigenetics suggest that our epigenome – the chemical changes that happen above our DNA sequence – might be the key to understanding and calculating human biological aging.
The distinction between biological and chronological age could have significant implications on how we should understand legal age. Currently, legal age, the age we have according to the law, always corresponds with chronological age. For example, a person chronologically 70, is by law, 70 years old. But now, suppose the person’s biological age turns out to be 50, why should her legal age correspond to her chronological rather than biological age? Many rights and duties depend on our official age, so how old we are, legally, is an important question that needs careful and detailed discussions by bioethicists, medical doctors, biologists and legal scholars among others.
Although little consensus exists on how exactly our biological age should be determined, different estimates have been proposed and used with promising results. Some estimates of biological age predict mortality or onset of age-related diseases more accurately than chronological age. For instance, a multibiomarker index of adult’s biological age outperformed their chronological age in predicting subsequent increased and clinically significant depressive symptoms. 
Arguably, epigenetic clocks,that measure DNA methylation in blood, are currently the most accurate and promising estimates of determining biological age.  For instance, major depression has been associated with higher epigenetic aging in blood as measured by DNA methylation patterns, suggesting that patients with major depression are biologically older than their corresponding chronological age.  Other research has shown the predictive utility of biological age for risk of disease; for every 5 years older a woman is in biological age than chronological age, her risk of breast cancer increases 15%.  It has been shown that epigenetic clocks predict all-cause mortality in later life better than chronological age.  These results indicate that epigenetic clocks relate strongly to a process that causes biological aging.
In an article published in the Journal of Medical Ethics, I started this academic discussion by outlining an argument for the legal age change.  I argued that when a person’s biological and chronological age differs, she could be allowed to change her legal age so that it corresponds with her biological rather than chronological age because doing so moves us closer to accurately measuring what chronological age is intended to measure. Age change should be allowed at least in cases when the person also feels that her legal age is not befitting and she is in danger of being discriminated against because of her legal age.
Since legal age change is something that has not been done before, it is natural that the first age change candidates are those who are harmed by ageism—discrimination due to age—either in the job market or elsewhere. Changing the legal age of a person to younger, ie. changing the date of birth, to better match her biological age, would thus likely to reduce the chances of being discriminated against because of her chronological age.
Some might reasonably suggest that ageism should be fought like racism and sexism are fought and, for instance, the date of birth should be something a job candidate should not be required to reveal to the employer in the first place. However, since racism and sexism still exist, it seems to me that we cannot get ageism to disappear with current policies. Some might think we should abandon the concept of age altogether. But age— even chronological age— is important for some people, thus banning people from revealing it seems unfair, even though it then could be hard to discriminate against people because of their age if job candidates were not allowed to tell or reveal their date of birth.  Since current measures against ageism are insufficient perhaps it is time to try something new: legal age change.
Currently chronological age is used as a proxy—an indicator of how well people function. While in some contexts chronological age might give a useful approximation of those characteristics that matter from the point of justice  it is far from clear that it is so in every context or in every specific case.  The results from research into epigenetics imply that it may soon be possible to calculate a person’s biological age accurately. When that happens, should our legal age still be based on low long we have existed—which seems to be irrelevant in many ways—rather than on how able and well-functioning we actually are?
Joona Räsänen MSSc, MSc
Affiliation: Department of Philosophy, Classics, History of Art and Ideas, University of Oslo, Norway
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