The global population is aging, driving up age-related disease morbidity. Antiaging interventions are needed to reduce the burden of disease and protect population productivity. Young people are the most attractive targets for therapies to extend healthspan (because it is still possible to prevent disease in the young). However, there is skepticism about whether aging processes can be detected in young adults who do not yet have chronic diseases. Our findings indicate that aging processes can be quantified in people still young enough for prevention of age-related disease, opening a new door for antiaging therapies. The science of healthspan extension may be focused on the wrong end of the lifespan; rather than only studying old humans, geroscience should also study the young. 
 
 Abstract 
 
 Antiaging therapies show promise in model organism research. Translation to humans is needed to address the challenges of an aging global population. Interventions to slow human aging will need to be applied to still-young individuals. However, most human aging research examines older adults, many with chronic disease. As a result, little is known about aging in young humans. We studied aging in 954 young humans, the Dunedin Study birth cohort, tracking multiple biomarkers across three time points spanning their third and fourth decades of life. We developed and validated two methods by which aging can be measured in young adults, one cross-sectional and one longitudinal. Our longitudinal measure allows quantification of the pace of coordinated physiological deterioration across multiple organ systems (e.g., pulmonary, periodontal, cardiovascular, renal, hepatic, and immune function). We applied these methods to assess biological aging in young humans who had not yet developed age-related diseases. Young individuals of the same chronological age varied in their “biological aging” (declining integrity of multiple organ systems). Already, before midlife, individuals who were aging more rapidly were less physically able, showed cognitive decline and brain aging, self-reported worse health, and looked older. Measured biological aging in young adults can be used to identify causes of aging and evaluate rejuvenation therapies. 

 If the school reunion was not proof enough, scientists have confirmed that people grow old at radically different rates, with some ageing much faster than their fresh-faced former classmates. 
 
 
 
 A study of nearly one thousand 38-year-olds found that while most had biological ages close to the number of birthdays they had notched up, others were far younger or older. 
 
 
 
 Researchers used 18 physiological markers, including blood pressure, organ function, and metabolism, to assess the biological age of each of the participants. For some, the past dozen years had taken no obvious toll on their body’s biology. 
 
 
 
 But others were not so fortunate. A good many participants had biological ages in the 50s, while one, described by scientists as an “extreme case”, had a biological age of 61 years old. That meant that for every birthday over the past dozen years, their body had aged three years. 
 
 “The overwhelming majority are biologically in their mid-40s or younger, but there are a handful of cases who are in pretty bad shape. In the future, we’ll come to learn about the different lives that fast and slow ageing people have lived,” said Daniel Belsky at Duke University in North Carolina. 
 
 
 
 The researchers drew on data gathered on 871 people enrolled in the Dunedin study, a major investigation that has tracked the health and broader lives of around 1000 New Zealanders born in 1972 or 1973 in the town of Dunedin, New Zealand. Of the original group, 30 had died by the age of 38 due to serious diseases such as cancer, or by accidents, suicides and drug overdoses. 
 
 
 
 “Our goal was to see if we can measure ageing in young people,” said Belsky. “It’s becoming increasingly clear that ageing is really the cause of much of the disease and disability burden we face, but our existing science is based on ageing in older people who already have a lot of age-related diseases.” 
 
 
 
 According to Belsky, studying ageing in younger people gives researchers the best chance of teasing apart the biological changes that drive ageing from those that underpin specific diseases. 
 
 
 
 The scientists drew up a list of 18 biological markers that together reflect a person’s biological age. They included measures of kidney and liver function, cholesterol levels, cardiovascual fitness and the lengths of teleomeres, which are protective caps that sit on the ends of chromosomes. 
 
 
 
 The set of markers were measured when the volunteers were aged 26, then 32, and finally at the age of 38. The researchers then looked to see how much the markers changed over time, to produce a “pace of ageing” figure. 
 
 
 
 Across the group, the biological ages of the 38-year-olds varied from 28 to 61. If a 38-year-old had a biological age of 40, it implied a “pace of ageing” of 1.2 years per year over the 12 year study period. Details of the study are published in Proceedings of the National Academy of Sciences. 
 
 
 
 “Even before they develop age-related diseases, their physiology shows signs, and there is great variation in how fast people ageed in the past 12 years,” Belsky said. 
 
 
 
 People with older biological ages fared worse on tests that are typically given to people over 60. These included tests of balance and coordination, but also mental tasks, such as solving unfamiliar problems. The biologically older people also reported more difficulties with activities like walking up the stairs. 
 
 
 
 The scientists went on to see whether volunteers’ biological ages matched how they old they looked. They invited students to view photos of the study participants and guess their ages. The biologically older people were consistently rated as looking older than their 38 years. 
 
 
 
 “Already, before midlife, individuals who were ageing more rapidly were less physically able, showed cognitive decline and brain ageing, self-reported worse health, and looked older,” the scientists write. 
 
 
 
 The next step in the research is to sift through the lives of the Dunedin participants to see how factors such as lifestyle, medical history, family circumstances, and stressful events might affect the speed at which people age. 
 
 
 
 Belsky called the study a “proof of concept” for using biological markers to measure the ageing process in people who are too young to have age-related diseases. An objective measure of biological age, he said, could be used to assess whether new anti-ageing therapies work or not in a reasonable time frame. 
 
 
 
 “What we need are measurements that can show whether these therapies are working, so we don’t have to wait 50 years to see if someone is still alive or not. We want a real-time barometer of how a peson is doing, and whether the therapy is really changing their rate of ageing,” he said. 
 
 
 
 The ultimate goal is to target ageing instead of the multiple separate diseases that people are increasingly likely to develop as they age. “As we get older, our risk grows for all kinds of different diseases. To prevent multiple diseases simultaneously, ageing itself has to be the target,” Belsky said. 
 

– If you've ever been told "you look good for your age," take it as the compliment it's meant to be—some people can't say the same. A study published in the Proceedings of the National Academy of Sciences finds people age at what the Guardian calls "wildly different rates," with biological ages not matching up to their chronological ones. Researchers studied 871 New Zealanders born in 1972 or '73 at the ages of 26, 32, and 38. Using a set of 18 biological markers such as blood pressure, cholesterol levels, and metabolism, scientists calculated each subject's biological age—and while most came in around where they should be, there were others who clocked in as either "younger" or "older." "The overwhelming majority are biologically in their mid-40s or younger, but there are a handful of cases who are in pretty bad shape," one of the study's authors says, per the Guardian. One "extreme case" had the unfortunate designation of basically being a 61-year-old, the paper notes. And those who ranked on the "older" side of things didn't just suffer the indignity of being given this label. "Already, before midlife, individuals who were [aging] more rapidly were less physically able, showed cognitive decline and brain [aging], self-reported worse health, and looked older," the researchers write. Why knowing who seems to age faster than others is important: Scientists hope to be able to study younger people's physiology for warning signs of diseases they haven't yet developed so that anti-aging therapies can be honed and maximized. "What we need are measurements that can show whether these therapies are working, so we don't have to wait 50 years to see if someone is still alive or not," the scientists say, per the Guardian. (A 3-year-old Oklahoma girl who doesn't appear to be aging at all still looks like a baby.)