"生育危机"真的只是危言耸听吗?

Are today's young men less fertile than their fathers were? It's a controversy in the fertility field, with some experts raising the alarm over what some are calling a 'sperm crisis' because they believe men's sperm counts have been decreasing for a decade or more.
当今青年男性的生育能力是不是弱于他们父辈年轻的时候？这是生育学领域中的一个争议话题。部分专家就一些人所说的“精子危机”发出了警告，因为他们相信，十多年来男性精子数一直在下降。

Experts here for the European Society of Human Reproduction and Embryology annual conference last week debated the issue for an entire day.
前不久，在欧洲人类生殖与胚胎学会(European Society of Human Reproduction and Embryology)的伦敦年会上，专家们围绕这个问题辩论了一整天。

One recent analysis found that in France, the sperm concentration of men decreased by nearly one-third between 1989 and 2005. Most but not all studies from several European nations with large databases and the ability to track health records have found that over the past 15 years or so, the counts of healthy men ages 18 to 25 have significantly decreased. This comes after a prominent study from the 1990s suggested that sperm count has decreased by half over the last half-century.
最近的一项分析发现，从1989年到2005年，法国男性精子密度下降接近三分之一。在多个拥有大型数据库、能够跟踪健康记录的欧洲国家，几乎所有研究都已经发现，在过去15年左右，18到25岁健康男性的精子数明显降低。上世纪90年代的一项著名研究也表明，之前半个世纪男性的精子数下降了一半。

Many experts questioned the validity of those findings. There are huge variations in results by country and region. Certain areas, especially in the developing world, haven't been studied at all. In the U.S., some historical data suggest a decrease in sperm count among American men, but no published recent data exist.
很多专家对这些结论的有效性提出质疑。不同国家和地区的结果千差万别，某些地区，特别是发展中国家根本就没有对此的研究。美国有一些历史数据表明该国男性精子数减少，但并没有近期数据发表。

Understanding if men are producing less sperm has implications beyond male fertility and couples who want children. The same environmental factors that might harm reproduction may also impact other parts of the body. Sperm count has even been linked with life expectancy, independent of cause of death.
弄清楚男性精子数有没有减少，其意义不仅仅止于男性生育能力问题和想要小孩的夫妻。可能有损生育能力的环境因素同样也有可能影响人体的其他部分。精子数甚至还被发现与预期寿命相关，不管死因是什么。

'It's a public health indicator,' says Joelle Le Moal, an epidemiologist at the French Institute for Public Health Surveillance near Paris.
巴黎附近的法国公共卫生监测研究所(French Institute for Public Health Surveillance)的流行病学家若埃勒・莫阿尔(Joelle Le Moal)说：“它是一个公共卫生指标。”。

Proponents say that exposure to pesticides, endocrine-disrupting chemicals like Bisphenol A and lifestyle habits like sitting for too long contribute to the proposed sperm crisis. And there is increasing evidence that sperm count, like other health conditions, may be influenced by what happens to people early in life, even in the womb.
支持者说，暴露于杀虫剂、双酚A等内分泌干扰物以及久坐不动之类的生活方式，都是所谓精子危机的造成因素。而且越来越多的证据表明，精子数和其他健康状况一样，也有可能受到生命早期、甚至是在子宫内所发生情况的影响。

'If our gametes, male or female, are not produced in the right manner, it could impact the next generation's health,' says Dr. Le Moal.
莫阿尔说：“如果我们配子（不管是精子还是卵子）的产生方式有问题，下一代的健康就有可能受到影响。”

In general, men produce upward of 60 million sperm per milliliter of semen. As long as the count is roughly greater than 40 million per ml, men are considered fertile and have the same chance of getting their partners pregnant as someone who produces a higher count.
总体上讲，男性一毫升精液的精子数在6,000万以上。只要每毫升精子数大致超过4,000万，男性就被认为具有生育能力。即使和某个精子数更高的人相比，其让伴侣受孕的概率也是一样的。

But below that threshold and particularly under about 20 million per ml, their ability to help conceive drops. It may take a couple longer than a year to conceive -- a problem known as subfertility -- or they may not succeed at all.
但如果低于这个门槛、特别是低于每毫升约2,000万的密度，那么他们让伴侣怀孕的能力就下降了。一对夫妻可能要花一年以上的时间才能怀上孩子──这被称为“弱育”(subfertility)问题──他们甚至还有可能根本就怀不上。

Not everyone in the field agrees a sperm crisis exists. Critics say that sperm concentration in a population is incredibly difficult to measure for a number of reasons, including the primary one of how to find men representative of the population. Tracking men who show up at a fertility clinic, for instance, would skew the results one way. Neither do sperm donors accurately stand for all the men in a region. Some recent studies have examined young men applying for military service, though the participation rate in the research tends to be low.
并不是生育学领域内所有人都认为有精子危机存在。批评者说，人群中的精子密度非常难以测量，原因有很多，首先便是如何找到人群中具有代表性的男性。比方说，如果是跟踪那些前往不孕不育医院就诊的男性，那么跟踪结果就有可能一边倒。捐精者也不能准确代表一个地区内的全部男性。近期曾有一些研究考察了申请参军的年轻男性，但这种研究的参与率往往不高。

In addition, there could be errors in measurement because of any number of immediate environmental factors, including the length of abstinence, scrotal temperature and time of year.
除此以外，由于禁欲时间、阴囊温度和季节等一个或多个直接的环境因素，也可能引起测量误差。

Stefan Schlatt, director of the Center for Reproductive Medicine and Andrology at the University of Munster in Germany, says he doesn't believe there is a sperm crisis world-wide. Even if sperm count decreased over time, it's unclear how many more men fall into the category of subfertile or infertile, Dr. Schlatt says.
德国明斯特大学(University of Munster)生殖医学与男科学中心(Center for Reproductive Medicine and Andrology)主任斯特凡・舒拉特(Stefan Schlatt)认为，并不存在一场世界范围的精子危机。舒拉特说，即使精子数确实是随着时间的推移而下降了，却也不会知道弱育或不育范畴的男性数量增加了多少。