Epidemiological evaluation on male reproductive function.

1.对精液质量变化的流行病学证据的批判性回顾我们评估了自1992年以来发表在医学杂志上的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严格审查，我们不能得出精液质量随时间推移而恶化的结论。日本供精者精液质量变化分析我们分析了1990-1998年在东京不孕症诊所就诊的325名日本供精者的10906份精液质量资料。精液浓度（所有数据）的回归系数为-1.16 x 106/ml/年，这可能表明精液浓度随时间推移而下降。然而，仅对每个供体的第一份样本进行类似分析，精液浓度的回归系数没有统计学显著性。对每种方法的前6个月中值的额外分析也未能显示显著结果。因此，我们的结论是，我们不能观察到日本精液捐献者在1990年至1998年的精液浓度显着下降。

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.