试想一下，当你参加大学毕业20周年同学会的时候，也许你会对同学们的变化产生疑问。尽管大家年龄相差不大，但彼此衰老的程度却不相同。

　　大多数关于衰老的研究，都聚焦于老年人。但是，来自美国、英国、以色列和新西兰的一个研究团队认为，要想预防衰老相关的疾病，应该对年轻人的衰老过程进行研究。他们利用了18项研究指标，联合测试出一个人是比同龄人老化得快还是慢。相关研究结果于近日发表在PNAS杂志上。

　　在这项研究中，954名实际参与者在他们26、32及38岁时，分别接受了18项分子标记物的测试。这些测试包括肾脏，肝脏，肺脏及代谢和免疫系统的功能。研究人员还检测了高密度脂蛋白、心肺功能和端粒的长度（端粒长度会随着年龄增加而缩短），以及牙齿的健康程度和眼底微小血管的情况（这项可代表大脑的血管情况）。根据这些测试结果，研究人员们可以绘出每一个变量的曲线图，这18项曲线图可以推断出每一个个体的衰老速度。大多数参与者与他们的实际年龄相当，然而，有些人每年实际衰老了3岁，有些人却并无衰老，后者这些"冻龄人"比他们的实际年龄要年轻。

　　此外，研究人员将这些参与者在38岁时的脸部照片，给Duke大学的本科生们看，并要求学生们根据这些参与者们看上去的年轻程度，排出顺序。调查结果显示，那些生物学上，内脏器官功能比较老的参与者，他们看上去也比较老。

　　衰老的过程并不全都是基因遗传决定，因为在对双胞胎衰老的研究中发现，只有20%的衰老归结于基因因素，外部环境影响也是巨大的。此项研究提供了一些方法，提示我们可以联合多项检查，推测衰老进程或者评估一些治疗衰老的效果。

　　doi: 10.1073/pnas.1506264112

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　　Quantification of biological aging in young adults

　　Daniel W. Belsky, et al.

　　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.