Becker S, Berhane K
Department of Population Dynamics, School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA.
Fertil Steril. 1997 Jun;67(6):1103-8. doi: 10.1016/s0015-0282(97)81446-x.
To re-examine data on sperm counts over time from 61 studies from around the world.
Parametric analyses and flexible nonlinear models of the relation between sperm counts and time.
MAIN OUTCOME MEASURE(S): Mean sperm concentrations per milliliter and regression coefficients for possible trends of concentrations over time.
RESULT(S): A significant decline was found only in U.S. studies.
CONCLUSION(S): Studies from specific sites have found declines in sperm counts, but a world-wide decline has not been demonstrated. Rigorous assessment of statistical models should be done before conclusions are drawn. Flexible smoothing models are a useful addition to currently available analytic methods.
重新审视来自世界各地61项研究中随时间变化的精子计数数据。
精子计数与时间关系的参数分析和灵活非线性模型。
每毫升的平均精子浓度以及浓度随时间变化的可能趋势的回归系数。
仅在美国的研究中发现显著下降。
特定地点的研究发现精子计数下降，但尚未证明全球范围内的下降情况。在得出结论之前，应对统计模型进行严格评估。灵活的平滑模型是对现有分析方法的有益补充。
