Joffe M
Department of Epidemiology and Public Health, Imperial College of Science, Technology and Medicine, St Mary's Hospital Medical School, London, UK.
Lancet. 1996 Jun 1;347(9014):1519-22. doi: 10.1016/s0140-6736(96)90673-x.
There has been much interest in the apparent decrease in semen quality. Because the evidence for such a decrease is open to criticism, a different type of evidence is needed. Finland seems to have escaped this decrease, as well as other disorders of the male reproductive tract, notably testicular cancer. If there has been a true decrease, the implications for fertility are unknown.
The most sensitive functional measure of fertility is time to pregnancy (TTP); this can be studied retrospectively at group level with a high degree of validity. To test the hypothesis that Finnish men are more fertile than British men, TTP distributions from published Finnish studies and data from Britain were compared. Two comparisons were made: a pair of antenatal studies, and a pair of cross-sectional studies.
In both comparisons, fertility was statistically significantly greater in Finland than in Britain. The findings did not seem to be due to methodological problems; in particular, the results could not be attributed to differences in frequency of intercourse, since this would have had the opposite effect on sperm concentration and on TTP.
The previously reported difference in sperm counts between Finland and elsewhere in northwest Europe (including Britain) is probably not artefactual, suggesting that the reported world-wide decline in semen quality is also real. Reasons for the "Finnish exception" may include maternal smoking, which used to be lower in Finnish women than elsewhere, and which might affect developing make offspring.
精液质量明显下降已引发诸多关注。由于支持这种下降的证据易遭批评，因此需要不同类型的证据。芬兰似乎未出现这种下降，也未出现男性生殖道的其他疾病，尤其是睾丸癌。如果确实出现了下降，其对生育能力的影响尚不清楚。
生育能力最敏感的功能指标是受孕时间（TTP）；这可以在群体层面进行回顾性研究，且具有较高的效度。为了检验芬兰男性比英国男性生育能力更强这一假设，对已发表的芬兰研究中的TTP分布与英国的数据进行了比较。进行了两项比较：一对产前研究和一对横断面研究。
在两项比较中，芬兰的生育能力在统计学上均显著高于英国。研究结果似乎并非由于方法学问题；特别是，结果不能归因于性交频率的差异，因为这对精子浓度和TTP会产生相反的影响。
先前报道的芬兰与欧洲西北部其他地区（包括英国）之间精子数量的差异可能并非人为造成的，这表明全球范围内报道的精液质量下降也是真实的。“芬兰例外”的原因可能包括母亲吸烟，过去芬兰女性的吸烟率低于其他地方，而这可能会影响发育中的男性后代。
