Historically, the science of epidemiology was directed toward identifying and controlling epidemics of infectious disease. In a study just published in the New England Journal of Medicine, my colleagues and I highlight another important job for epidemiologists: identifying and controlling epidemics of medical care.
历史上，流行病学的研究方向是确诊和控制广泛传播的传染病。我和同事们在《新英格兰医学杂志》(New England Journal of Medicine)上刚刚发表的一篇研究论文中指出，流行病专家还有另外一项任务：识别和控制医疗界造成的流行病。

The setting is South Korea, where, over the last two decades, the incidence of thyroid cancer has increased fifteenfold. Nowhere in the world is the rate of any cancer growing faster.
研究的背景是韩国。在过去20年里，这里甲状腺癌的发病率提高到了最初的15倍。全世界任何地方都没有哪种癌症能如此之快地增长。
We’ve all been taught to seek biological explanations for a significant rise in disease — perhaps a new infectious agent or environmental exposure. But in South Korea, we are seeing something different: an epidemic of diagnosis.
我们受过的教育都是，为发病率的显著提高寻找生物学上的解释，或许是新的病原体，或许是环境暴露。然而在韩国，我们看到了不同的情况，这种流行病是因为诊断造成的。
In 1999 the government initiated a national health-screening program focused on reducing cancer and other common diseases. Although thyroid cancer screening was not included in the program, all it requires is a simple test — an ultrasound of the neck. Hospitals have ultrasound machines and so do many doctors’ offices. Both promoted thyroid cancer screening as an inexpensive add-on to the government program. It was an easy sell, particularly with the government, the medical community, the news media and cancer “survivors” praising the virtue of early cancer detection.
1999年，韩国政府启动了一项全国性的体检计划，主要目的是减少癌症和常见病。尽管其中并不包括甲状腺癌筛查，但它只需要一个简单的步骤：颈部超声波检查。医院里有超声波设备，很多医生的诊所里也有。医院和医生都认为，它是政府计划之外一项廉价的补充检查，因而鼓励患者检查。而患者也很乐于接受，尤其是因为政府、医疗界、新闻媒体和癌症“生还者”都称赞，及早发现癌症有好处。
In doing so they inadvertently highlighted the major harm of early detection: What was a rare cancer is now the most common cancer in South Korea.
但这样做也意外地突显了及早诊断的巨大危害：一种本来罕见的癌症，成为了韩国最常见的癌症。
Where did all those new thyroid cancers come from? They were always there. As early as 1947 pathologists recognized that, although it was a very rare cause of death, thyroid cancer was a frequent finding during autopsies. Studies have since shown that over a third of adults have thyroid cancer. Virtually all of these cancers are small “papillary thyroid cancers,” many of which will never become evident during a person’s life.
那些新增的甲状腺癌患者是从哪里来的呢？他们其实一直存在。早在1947年，病理学家就发现，尽管极少成为死因，但是在尸检中经常发现死者患有甲状腺癌的情况。从那时起，研究就发现，超过三分之一的成年人患有甲状腺癌。其中几乎所有人患的都是微小的“甲状腺乳头状癌”，许多人一生中症状都不明显。
Unless that person receives a screening ultrasound. In fact, virtually all the newly identified thyroid cancers in Korea are papillary thyroid cancers. How do we know this is not a real epidemic of disease? Because the number of Koreans dying from thyroid cancer has not changed. If the screening were saving lives, the death rate would decline, or increase more slowly as the epidemic spread — but not stay perfectly flat.
除非这个人接受了超声波检查。事实上在韩国，几乎所有新确诊的甲状腺癌都是乳头状癌。我们怎么才能知道这不是真正的流行病呢？因为在韩国，死于甲状腺癌的人数并没有变化。如果超声检查挽救了患者的生命，那么死亡率应该降低才对，而如果流行病蔓延开来，死亡率应该缓慢上升才对——然而数据却完全没有起伏。
An epidemic of diagnosis is not good for anyone’s health. Resources are needlessly diverted; people are needlessly scared. But the biggest problem is that it begets an epidemic of treatment.
诊断呈现的流行病对任何人的健康都没有好处，而且它毫无必要地转移了资源，也毫无必要地惊吓了患者。然而最大的问题是，它在医疗体系内催生了过度治疗。
The majority of patients given diagnoses of thyroid cancer have their thyroid gland removed. The thyroid is an important gland — it produces the hormones that control metabolism. Without it, patients may need lifelong thyroid replacement therapy. And it can take doctors a while to find the right dose for each individual. In the meantime, patients suffer from the effects of too little or too much thyroid hormone, including energy and weight fluctuations.
多数被诊断患有甲状腺癌的患者，被切除了甲状腺。然而甲状腺是一个重要的腺体，它能分泌控制新陈代谢的激素。如果切除了，患者就可能会终生需要甲状腺替代治疗，而且医生可能需要一段时间才能为每一位患者找到恰当的剂量。与此同时，患者还要承受甲状腺素水平过低或过高的后果，包括精力和体重的波动。
The surgery has other less common complications. In South Korea and the United States about 10 percent of patients have problems with calcium metabolism and about 2 percent experience vocal cord paralysis. And, as with any surgery, there can be life-threatening effects — blood clots in the lungs, heart attacks and strokes. In about two of every 1,000 thyroid cancer operations, the patient dies. It’s rare, but it happens.
这种手术也会产生一些并不十分常见的并发症。在韩国和美国，大约10%的患者产生了钙质代谢问题，约有2%的患者发生了声带麻痹。此外，就像任何一种手术一样，它可能会产生威胁生命的后果，如肺部血凝块、心肌梗死和中风。每一千例甲状腺癌手术中，大约会有两名患者身亡。很罕见，但的确会发生。
Could what happened in South Korea happen here? Absolutely. Even without a concerted effort to promote screening, thyroid cancer incidence in the United States is up threefold since 1975. To reverse this trend, we need to actively discourage early thyroid cancer detection.
在韩国发生的情况也会在美国发生吗？绝对会。尽管没有各方同心协力推动筛查，美国的甲状腺病例自1975年以来也已经提高到了最初的三倍。要想扭转这种趋势，我们需要积极地劝阻甲状腺癌的早期检查。
The virtue of early detection is so ingrained and so appealing that many assume that screening can only be good for you. But that’s not true. The Korean experience illustrates the downside of trying to find cancer early: overdiagnosis and overtreatment. The problem is greatest for thyroid and prostate cancer, but also exists for cancers of the lung, breast, skin and kidney. And then there is all the angst surrounding screening — that can’t be good for anyone’s health.
及早检查有好处的观念根深蒂固，而且也很吸引人，所以许多人都认为，做一下检查只会有好处。然而事实并非如此。韩国的经验显示出，试图早期诊断癌症的做法有负面的影响：过度诊断和过度治疗。甲状腺癌和前列腺癌的问题最为严重，然而对肺癌、乳腺癌、皮肤癌、肾癌也存在。当然还有对于检查的焦躁，这可是对任何人的健康都不会有好处的。
Of course, screening makes sense in some situations: in particular for people who are at a genuinely high risk for the cancer — those with multiple cancer deaths in their family history. People at average risk who expect to live long enough to experience the potential benefit in the future — and who are willing to accept the chance of harm from unneeded treatment now — may also decide that the screening makes sense for them.
当然，检查在一些情况下是有意义的，尤其是癌症真正的高危患者：家族内有多人死于癌症的患者。患病风险中等，但预期寿命足够长，未来可以体验到潜在收益的人——以及那些愿意接受现在并不需要的治疗带来的受到损害的可能性的人——或许也会认定接受检查是合理的。
Nevertheless, those interested in early detection may want to concern themselves with the question of how early. Sure, we would rather diagnose cancer in a small breast lump than wait until it develops into a large breast mass. But it may be excessive to extrapolate from that to searching for microscopic cancers. Many of the thyroid cancers found in South Korea were less than a centimeter in size. If we look for earlier cancers, we will always find more. And, at some point, we identify too many things that are better off left unfound. In short, having doctors not look too hard for early cancer is in your interest.
尽管如此，有兴趣及早检查的人们，也应该考虑一下多早算早的问题。当然，我们宁愿早些诊断微小的乳腺肿块是不是癌症，也不愿意坐视它发展成大肿块。但如果就此推论，应当寻找显微镜才能看到的微小肿块，恐怕就过头了。韩国发现的许多甲状腺癌变的尺寸不足一厘米。如果我们去寻找癌变的话，总能发现更多病例。但超过了一个限度，我们确诊出的问题就太多了，还不如让它们留在那里不被发现好。简而言之，让医生不要那么热衷于发现早期的癌变，符合患者的利益。
That’s where epidemiology comes in. Too many epidemiologists concern themselves not with controlling infectious disease, but with hoping to find small health effects of environmental exposures — or worse, uncertain effects of minor genetic alterations. Perhaps they should instead monitor the more important risk to human health: epidemics of medical care.
这正是流行病学的意义。太多的流行病专家不是关注于控制传染病，而是希望寻找环境暴露因素对健康产生的微小影响，更糟的是，寻找微小基因差异可能产生的影响。或许他们应该去关注人类健康更重要的风险：医疗界造成的流行病。