Objectives Considerable interest and controversy over a possible decline in semen quality during the 20th century raised concern that semen quality could have reached a critically low level where it might affect human reproduction. The authors therefore initiated a study to assess reproductive health in men from the general population and to monitor changes in semen quality over time.
Design Cross-sectional study of men from the general Danish population. Inclusion criteria were place of residence in the Copenhagen area, and both the man and his mother being born and raised in Denmark. Men with severe or chronic diseases were not included.
Setting Danish one-centre study.
Participants 4867 men, median age 19 years, included from 1996 to 2010.
Outcome measures Semen volume, sperm concentration, total sperm count, sperm motility and sperm morphology.
Results Only 23% of participants had optimal sperm concentration and sperm morphology. Comparing with historic data of men attending a Copenhagen infertility clinic in the 1940s and men who recently became fathers, these two groups had significantly better semen quality than our study group from the general population. Over the 15 years, median sperm concentration increased from 43 to 48 million/ml (p=0.02) and total sperm count from 132 to 151 million (p=0.001). The median percentage of motile spermatozoa and abnormal spermatozoa were 68% and 93%, and did not change during the study period.
Conclusions This large prospective study of semen quality among young men of the general population showed an increasing trend in sperm concentration and total sperm count. However, only one in four men had optimal semen quality. In addition, one in four will most likely face a prolonged waiting time to pregnancy if they in the future want to father a child and another 15% are at risk of the need of fertility treatment. Thus, reduced semen quality seems so frequent that it may impair the fertility rates and further increase the demand for assisted reproduction.
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Review history and Supplementary material
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To cite: Jørgensen N, Joensen UN, Jensen TK, et al. Human semen quality in the new millennium: a prospective cross-sectional population-based study of 4867 men. BMJ Open 2012;2:e000990. doi:10.1136/bmjopen-2012-000990
Contributors Substantial contributions to conception and design: NJ, TKJ, A-MA, JT and NES. Acquisition of data: NJ, UNJ, TKJ, MBJ, IAO, AJ and EC. Analysis of data: NJ, UNJ, KA, JHP and NES. Interpretation of data: all authors. Drafting the article: NJ, UNJ and NES. Revising the article critically for important intellectual content: all authors. Final approval of the version to be published: all authors.
Funding This study has been supported economically by several grants: the European Union (contract numbers BMH4-CT96-0314, QLK4-CT-1999–01422, QLK4-CT—2002–00603 and most recently FP7/2007–2013, DEER Grant agreement no. 212844), the Danish Research Council (grants numbers 9700833 2107-05-0006), the Danish Agency for Science, Technology and Innovation (Grant number 271070678), Rigshospitalet (Grant number 961506336), the University of Copenhagen (Grant number 211-0357/07-3012), the Danish Ministry of Health and the Danish Environmental Protection Agency, A.P. Møller and wife Chastine McKinney Møllers foundation and Svend Andersens Foundation. The funding organisations played no role in the design and conduct of the study; in collection, management, analysis and interpretation of the data; or in the presentation, review or approval of the manuscript.
Competing interests None.
Ethics approval The local Science Ethical Committee had approved the study (June 1996, the Science Ethical Committee for the Copenhagen and Frederiksberg municipalities, reference number KF01-117/96, and most recently June 2011, the Capital Region of Denmark, reference number H-KF-289428), and all participants had given their informed consent.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement There are no additional data available.
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