Epidemiological evaluation on male reproductive function.

1. 对精液质量变化的流行病学证据的重要回顾我们评估了1992年以来发表在医学期刊上的关于精液质量变化的报告，以了解精液质量是否随着时间的推移而恶化。结果，一些人报告精液质量下降，但另一些人报告精液质量没有变化。地理和季节变化以及测量误差可能在很大程度上导致精液质量的变化。因此，通过对最近流行病学研究的批判性回顾，我们不能得出精液质量随着时间的推移而恶化的结论。日本捐精者精液质量变化的分析我们分析了1990-1998年在东京不育诊所就诊的325名日本捐精者的10906份精液质量数据。精液浓度（所有数据）的回归系数为-1.16 × 106/ml/年，这可能表明精液浓度随着时间的推移而下降。然而，仅对每个供者的第一个样本进行类似分析，精液浓度的回归系数没有统计学意义。另外的分析中位数为前6个月，也没有显示出显著的结果。因此，我们得出结论，在1990- 1998年期间，我们没有观察到日本精液供体的精液浓度显著下降。

1. Critical review of epidemiological evidence on changes in semen qualityWe evaluated reports on changes in semen quality published on medical journals since 1992 to see whether semen quality has been deteriorated or not over time. As a result, some reported decline in semen quality, but others reported as unchanged. Geographical and seasonal variations as well as measurement error may largely contribute to changes in semen quality. Therefore, with critical review of recent epidemiological studies, we could not conclude that semen quality has been deteriorated over time.2. Analysis of changes in semen quality of Japanese semen donor samplesWe analyzed 10906 semen quality data from 325 Japanese semen donors who visited infertility clinic in Tokyo in 1990-1998. A regression coefficient for semen concentration (all data) was-1.16 x 106/ml/year, which might indicate that semen concentration has been declined over time. However, similar analysis with the first sample of each donor only, a regression coefficient for semen concentration was not statistically significant. Additional analysis with median value of first 6 months for each also failed to show significant results. Thus, we conclude that we could not observe significant decline in semen concentration of Japanese semen donors in 1990-98.