Bonde J P, Kold Jensen T, Brixen Larsen S, Abell A, Scheike T, Hjollund N H, Kolstad H A, Ernst E, Giwercman A, Skakkebaek N E, Keiding N, Olsen J
Department of Occupational Medicine, Aarhus University Hospital, Denmark.
Scand J Work Environ Health. 1998 Oct;24(5):407-13. doi: 10.5271/sjweh.362.
Several reports indicate a secular decline of human sperm counts. It is still not known if these findings are artifacts related to shortcomings in the data and applied methodologies. Even less is known about possible mechanisms, but it has been proposed that potential changes may be related to disruption of the hormonal regulation of testicular development in prenatal life. The objective of this study was to examine whether sperm count was related to year of birth.
An analysis was made of the sperm count of 1196 men participating in 10 cross-sectional occupational sperm studies in 3 regions of Denmark from 1986 through 1995.
The median sperm concentration was 63 million per milliliter for men born in 1937-1949 and 52 million per milliliter for men born in 1970 or later, and the median total sperm was 206 million and 117 million, respectively. The inverse relationship between sperm concentration and year of birth was statistically significant even after adjustment for duration of sexual abstinence, season of the year, and study population. However, bias because of differential participation related to age and fertility or lack of comparability across the populations cannot be ruled out.
The apparent decline of sperm count with increasing year of birth is compatible with the hypothesis of a common risk factor for male reproductive health operating in prenatal life or early childhood, but the evidence is circumstantial. Age-related selection bias is an alternative and perhaps not a less likely explanation.
多项报告表明人类精子数量呈长期下降趋势。目前仍不清楚这些发现是否是与数据及应用方法的缺陷相关的人为现象。对于可能的机制了解更少，但有人提出潜在变化可能与产前生活中睾丸发育的激素调节紊乱有关。本研究的目的是检验精子数量是否与出生年份有关。
对1986年至1995年期间丹麦3个地区参与10项横断面职业精子研究的1196名男性的精子数量进行了分析。
1937 - 1949年出生男性的精子浓度中位数为每毫升6300万，1970年及以后出生男性的精子浓度中位数为每毫升5200万，总精子数中位数分别为2亿600万和1亿1700万。即使在对性禁欲持续时间、年份季节和研究人群进行调整后，精子浓度与出生年份之间的负相关在统计学上仍具有显著意义。然而，不能排除因年龄和生育能力导致的不同参与度或人群间缺乏可比性所造成的偏差。
随着出生年份增加精子数量明显下降，这与产前生活或幼儿期存在影响男性生殖健康的共同危险因素这一假设相符，但证据是间接的。与年龄相关的选择偏差是另一种解释，而且可能性或许并不小。
