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Global trends in semen quality of young men: a systematic review and regression analysis

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Abstract

Purpose

Many studies have reported declines in semen quality mainly focused on total sperm counts (TSC) and sperm concentration (SC), ignoring the importance of progressive motile sperm (PR), total motile sperm (TM), and normal morphological sperm (NM). Therefore, we performed a comprehensive meta-analysis to explore the trend in semen quality of young men.

Methods

We searched 3 English databases and 4 Chinese databases from January 1980 to August 2022. Random-effect meta-analyses and weighted linear regression models were conducted to perform the trend in semen quality.

Results

Finally, 162 eligible studies including 264,665 men from 28 countries were got between 1978 and 2021. Significant decreases were observed in TSC (− 3.06 million/year, 95% CI − 3.28 to − 2.84), SC (− 0.47 million/ml/year, 95% CI − 0.51 to − 0.43), and PR (− 0.15%/year, 95% CI − 0.20 to − 0.09), and there was an upward trend in TM (0.28%/year, 95% CI 0.24 to 0.32). The results of meta-regression analyses indicated that age, continent, income, WHO criteria, and abstinence time significantly impacted on TSC, SC, PR, and TM. Positive regression coefficients were observed in some categories suggesting that outcomes might not be declining and even increasing in these subgroups.

Conclusions

Downward trends in semen quality among global young men were observed in our study, including TSC, SC, and PR. But TM did not appear to be trending down or even to be leveling off. More studies are needed to focus on the causes of the declines.

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Author information

Authors and Affiliations

  1. Department of Reproductive Andrology & Sichuan Human Sperm Bank, West China Second University Hospital, Sichuan University, Chengdu, China

    Xuefeng Luo & Chengchao Du

  2. Key Laboratory of Birth Defects and Related Diseases of Women and Children, Sichuan University, Ministry of Education, Chengdu, China

    Xuefeng Luo, Chengchao Du & Xiangcheng Pan

  3. School of Big Data and Artificial Intelligence, Chengdu Technological University, Chengdu, China

    Chongyang Yin

  4. Department of Pharmacy, West China Second University Hospital, Sichuan University, Chengdu, China

    Yuqing Shi & Xiangcheng Pan

  5. Evidence-Based Pharmacy Center, West China Second University Hospital, Sichuan University, Chengdu, China

    Yuqing Shi & Xiangcheng Pan

  6. West China School of Pharmacy, Sichuan University, Chengdu, China

    Yuqing Shi & Xiangcheng Pan

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Contributions

XFL and XCP designed this meta-analysis together. XFL and CYY were responsible for the inclusion and exclusion of the article. CYY and YQS gathered and processed the data. XFL and CCD made the quality assessment. XCP was responsible for data acquisition and performed data analysis with CYY. XFL and XCP drafted the article and revised the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Xiangcheng Pan.

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Key questions

What is already known on this topic?

Many studies have reported declines in TSC and SC, while some authors hold the opinion that worldwide sperm counts are not declining. What is more, sperm motility and morphology are not taken into consideration.

What are the new findings?

In this study, we performed a comprehensive meta-analysis to explore the trend in semen quality of young men. Total 162 eligible studies including 264,665 men from 28 countries were got between 1978 and 2021. The downward trends in semen quality among global young men were observed in our study, including TSC, SC, and PR, but TM did not appear to be trending down or even to be leveling off.

What do the new findings imply?

Overall, our study demonstrated that the semen quality of global young men is declining, and more studies are needed to focus on the causes of the declines on the future.

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Luo, X., Yin, C., Shi, Y. et al. Global trends in semen quality of young men: a systematic review and regression analysis. J Assist Reprod Genet 40, 1807–1816 (2023). https://doi.org/10.1007/s10815-023-02859-z

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  • DOI: https://doi.org/10.1007/s10815-023-02859-z

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