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你的身体并非为长久而造：人类死亡率数据的一课
Your body wasn’t built to last: a lesson from human mortality rates
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导读
文章从人类死亡率随年龄变化的统计规律出发，解释身体并非为长久使用而设计：年轻时死亡风险较低，之后随年龄近似指数上升，像复杂系统在不断累积损伤。作者用模型和比喻说明，衰老可以理解为未修复损伤逐步积累的结果。
为什么经久不衰：它用简洁的统计模型把衰老变成可讨论的工程问题，今天读仍能连接可靠性理论、癌症研究与长寿讨论。
HN 评论精选
用可靠性工程看待衰老，主张通过修复累积损伤延长健康期。
身体可视为由许多冗余组件组成的系统，衰老是这些组件不断累积未修复损伤的结果。这个模型很好用；一旦按损伤与修复的思路思考，就会走向 SENS 这类通过增量修复延长身体黄金运行期的研究计划。
reasonattlm查看英文原文
The body can be considered as a system of many redundant components, with aging as the result of progressive unrepaired damage to those components. This is a model that works very well. For further reading, you might look at the application of reliability theory to aging: http://www.fightaging.org/archives/2010/05/applying-reliability-theory-to-aging.php http://en.wikipedia.org/wiki/Reliability_theory_of_aging_and_longevity Once you start to think along the lines of damage and repair, you inevitably end up in the SENS camp. It's the logical place to be. http://www.fightaging.org/archives/2006/11/the-engineers-viewpoint-treat-change-as-damage.php Bodies are complex systems and all complex systems can be prolonged in their period of prime operation by sufficiently diligent incremental repair. Developing a toolkit to do that for humans is the point of SENS the research program, with the point of SENS the advocacy program being to help people understand that the scientific community well understands in detail what needs repairing. For more on the biochemistry of damage-that-causes-aging, explained for laypeople, you might look here: http://www.sens.org/sens-research/research-themes
原文把泊松分布与指数衰减混淆了，应区分二者。
小纠正：在“随机闪电”情景下，活到年龄 t 的生存概率服从指数分布；泊松分布是离散的，且是阶乘衰减，不是指数衰减。
willchang查看英文原文
> Anyone who paid attention during introductory statistics will recognize that your probability of survival to age t would follow a Poisson distribution, which means exponential decay (and not super-exponential decay). Small correction: survival to time t under the lightning bolt scenario follows an exponential distribution. A Poisson distribution, besides for being discrete, has factorial decay, not exponential decay.
延长寿命还需考虑心理与哲学后果，可能出现新的精神疾病。
身体寿命能否大幅延长尚有争议，但人们很少讨论“无限期活着”的哲学与心理影响。即使身体相对年轻，精神疾病怎么办？正如延长寿命暴露出癌症等过去未知的疾病，进一步延长寿命是否也可能暴露我们无法想象的新状况，甚至纯心理问题？人们真的想活几百年吗？
angdis查看英文原文
The longevity of the body is one thing, it is debatable whether or not it can be extended by a lot or a little (or at perhaps until the MTBF of a freak accident). What I rarely see discussion of, however, are philosophical and psychological implications of "living indefinitely". Even if the body is says relatively youthful, what about diseases of the mind? In other words, I am saying that in the same way that increasing life-span has uncovered a plethora of diseases that were previously unknown like cancer, is it possible that further increasing life span may uncover conditions (perhaps purely psychological) that we can't even imagine. Will people _want_ to live 100's of years?
癌症是累积随机突变的结果，死亡原因多样，不能过度解读单一模型。
作为癌症生物学家，我可以说至少有些假设不成立。急性髓系白血病完全由“累积的闪电”驱动：血液干细胞每次分裂，DNA 都会随机出现少量复制错误；若一个细胞在错误基因中累积两三个这种突变，就会发展成 AML，活得越久越可能发生。归根结底，活得足够久的人最终都会得癌症。这些图很有趣，但不深入思考大量死亡方式就读太多很危险，许多死亡方式的年龄分布截然不同。
chrisamiller查看英文原文
As a cancer biologist, I can tell you that at least some of these assumptions don't hold true. Acute Myeloid Leukemia is driven entirely by "accumulated lightning bolts". Every time your blood stem cells divide, a small number of replication errors occur randomly in the DNA. If one of these cells accumulate two to three of these mutations in the wrong genes, you will develop AML. The longer you live, the more likely it is that this will occur. Bottom line, everyone who lives long enough will eventually get cancer. While I agree that these plots are interesting, it's dangerous to read too much into these without thinking more deeply about the vast number of ways that there are to die, many of which will have strikingly different age distributions. (see http://www.sciencedirect.com/science/article/pii/S0092867412007775)
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