Semen quality evaluation in a cohort of 28213 adult males from Sichuan area of south-west China

Spatiotemporal trends in human semen quality

Over the past four decades, studies of various designs have reported spatial and temporal trends in human semen quality. Several standardized-methodology studies in homogeneous populations that compare specific cities within a country or a continent provide clear evidence of geographical differences in sperm production, even over short distances within the same country. Human sperm production is widely believed to be declining over time, but evidence from the scientific literature is less clear. Studies based on repeated cross-sectional data from a single centre have shown mixed results. Among the numerous retrospective studies conducted in a single centre, only some included homogeneous groups of men and appropriate methods, and most of them suggest a temporal decrease in human sperm production in the geographical areas considered. Conclusions reporting temporal trends in sperm production that came from existing retrospective multicentre studies based on individual semen data and those using means, medians or estimates of sperm production are questionable, owing to intrinsic limitations in the studies performed. Regardless of study design, studies on the percentage of motile or morphologically normal spermatozoa are still limited by the inherent variability in assessment. Overall, available data do not enable us to conclude that human semen quality is deteriorating worldwide or in the Western world, but that a trend is observed in some specific areas. To understand these trends and contrasts in sperm and semen quality, prospective studies should be encouraged and combined with assessment of the male exposome.

Several studies over the past few decades have suggested that sperm quality varies by geographical region and might be subject to a temporal decline worldwide. However, the data supporting these conclusions have come from studies of various methodologies and heterogeneous populations, making them unreliable. In this in-depth Review, Chevrier and colleagues discuss the data surrounding discussion of spatiotemporal trends in semen parameters and consider how these trends and the factors promoting them interact.

The vast literature on human semen quality trends is extremely heterogeneous in terms of the populations studied and study designs, and so these studies have been unable to draw firm conclusions.

Understanding the data around spatiotemporal semen trends requires a focus on the methodological choices and application of criteria to filter findings from the studies with optimal design.

Numerous appropriately designed studies suggest unambiguous geographical contrasts in human sperm production; however, evidence of a decline in sperm production is reliable only in specific populations and cities in which studies with a complete set of quality criteria have been conducted.

By contrast, suggestions of a worldwide drop in human semen quality on the basis of retrospective multicentre studies cannot be substantiated, owing to intrinsic limitations in the studies performed.

Many and varied factors of variation, in particular the diverse modalities of assessment, do not enable us to conclude that clear temporal trends of sperm motility and normal morphology are present.

Progress in our understanding of the highlighted trends and their causal factors requires prospective studies that minimize all known biases combined with the assessment of men’s exposome.

Study of Semen Quality, Reproductive Hormone Levels, and Lipid Levels in Men From Arkhangelsk, a City in North of European Russia

Male populations in the European North of Russia have not previously been investigated for semen quality. The aim of this study was to evaluate semen parameters, reproductive hormone levels, and lipid levels in volunteers from the general urban population of the European North of Russia, to compare the data published for men from the neighboring Northern or Eastern European countries, and to evaluate associations between sperm quality and serum hormonal and lipid levels. Ninety-nine volunteers aged 23-63 years residing in the city of Archangelsk were enrolled in the study. All men had blood samples drawn and completed a questionnaire concerning their health status and lifestyle; 90 men delivered semen samples. The medians for semen volume, sperm concentration, progressive motility, and normal morphology were 3.0 ml, 42.12 million/ml, 43.8%, and 6.5%, respectively. Sperm parameters below normal threshold values were found in 38.9% of participants. It seems that the sperm quality in our study group was slightly worse than in men from Finland, Norway, Sweden, or Estonia, but very similar to that in men from Denmark or Poland. The significant negative correlations of luteinizing hormone levels and positive correlations of inhibin B levels with sperm concentration and progressive motility were revealed. Higher levels of luteinizing hormone and lower levels of inhibin B were found in participants with impaired compared to normal sperm quality. No reliable links were found between serum total cholesterol, triglyceride, high and low-density lipoprotein cholesterol, and semen parameters.

A longitudinal study of semen quality among Chinese sperm donor candidates during the past 11 years

Studies suggest that semen quality is declining globally, however, the debate remains open due to the possible effects of ethnic and geographical differences. This study aimed to explore whether semen quality of sperm donor candidates has changed in Henan Province, China from 2009 to 2019. In this retrospective study, we included 23,936 sperm donor candidates who were recruited by the Henan Human Sperm Bank of China between 2009 and 2019. To minimize intra-individual bias, we included only the first ejaculate provided by each sperm donor candidate. The following parameters were measured: volume, sperm concentration, total sperm count, progressive motility, and total motility. After adjustment for age, body mass index (BMI), and sexual abstinence duration, we evaluated changes in main semen parameters over time using multiple linear regression analyses. The sperm concentration decreased from 62.0 million/mL in 2009 to 32.0 million/mL in 2019 (P < 0.001), with an average annual rate of 3.9%. The total sperm count decreased from 160.0 million in 2009 to 80.0 million in 2019 (P < 0.001), with an average annual rate of 4.2%. The progressive motility decreased from 54.0% in 2009 to 40.0% in 2019 (P < 0.001), with an average annual rate of 2.5%. The total motility decreased from 60.0% in 2009 to 46.0% in 2019 (P < 0.001), with an average annual rate of 1.9%. Our results indicated that semen quality among sperm donor candidates had decreased during the study period in Henan Province, China.

Decline in semen concentration of healthy Chinese adults: evidence from 9357 participants from 2010 to 2015

The present study aims to analyze sperm concentration trends among young and healthy Chinese adults in Wuhan, Central China, from 2010 to 2015. Semen analysis data from 9357 participants were collected and analyzed using a general linear model and the Cochran–Armitage trend test. A significant decline was observed in sperm concentration (β [standard deviation]: −1.53 [0.16]; P < 0.001). In addition, a decline in sperm density was observed by stratifying student versus nonstudent sperm donors and by analyzing the year of birth or birth year cohort of the participants. Furthermore, the percentage of participants with sperm densities of over 40 × 10⁶ ml⁻¹ significantly decreased with year. Notably, a dramatic decline in sperm density was recorded over the first 5 years of study. This research reported a decline in sperm concentration among young adults in Wuhan, Central China, in 2010–2015.

Declining Sperm Counts… or Rather Not? A Mini Review

Importance

Temporal global trends of sperm quality remain a matter of debate.

Objective

The aim of this study was to present a comprehensive review of studies reporting on sperm quality counts, summarize the main end points, and assess the main reasons for potential discrepancies.

Evidence Acquisition

An evidence-based review of PubMed and Scopus databases was performed regarding studies reporting on modification of sperm quality counts, independently of study character, study language, or date.

Results

Since the meta-analysis of Carlsen et al in 1992 (Br Med J 1992;305:609-613) that suggested an annual decline in sperm count of 1%, several reports confirmed the decline in sperm quality, whereas others disproved them, suggesting a slight increase or absence of change in sperm count. Such controversies may be attributed to geographical and time-related variability in sperm values and also to several confounding factors that influence the semen parameters. Intrinsic weaknesses of the studies include heterogeneity of subjects recruited, lack of adjustment for confounding factors, and samples that do not always represent the general population.

Conclusions

No consensus exists on whether sperm counts actually decrease because studies' results are often controversial or inconclusive with methodological deficiencies. More prospective, large-scale, population based studies are needed in order to provide sound evidence of possible global trends in sperm count.

Exposed Biologies and the Banking of Reproductive Vitality in China

The looming figures of smog-choked cities, cancer villages and contaminated food have become iconic of a modernising China: the tragic, perhaps unavoidable, side effects of a voracious economy. In this article, I examine how the sperm bank—jingzi ku—in China has emerged quite literally as a sanctuary of vitality amidst concerns around food safety, air and water pollution, rising infertility and declining population quality. As a twist on Margaret Lock’s concept of ‘local biologies’, I argue that ‘exposed biologies’ have become a matter of concern in China in ways that have corroborated a place for hi-tech sperm banks within China’s restrictive reproductive complex. Exposed biologies are a side effect of modernisation processes, as industrially manufactured chemicals are increasingly held culpable for a range of pathologies, from cancers to metabolic diseases, disorders of sex development and infertility. Amidst concerns that pollution and modern lifestyles are deteriorating sperm quality in China, the sperm bank stands out as a repository of screened, purified and quality-controlled vitality, and as such sperm banking can be seen as a form of reproductive insurance, not only for individuals but also for the nation.

Decline of semen quality among Chinese sperm bank donors within 7 years (2008-2014)

Semen from 5210 sperm bank donors was analyzed and trends in semen quality were evaluated at Shandong Human Sperm Bank between 2008 and 2014. After 2-7 days of abstinence, semen samples were collected. Measurements of semen volume, sperm concentration, sperm forward motility, and total sperm count were performed. There were significant declining trends in semen volume, sperm concentration, sperm forward motility, and total sperm count. Our results indicate that the quality of semen in this cohort of sperm donors had decreased during the study period.

Decline in semen quality among 30,636 young Chinese men from 2001 to 2015

OBJECTIVE

To provide information of semen quality among young Chinese men in the past 15 years.

DESIGN

Retrospective cross-sectional study.

SETTING

Sperm bank.

PATIENT(S)

A total of 30,636 young adult men who applied to be sperm donors at the Hunan Province Human Sperm Bank of China in 2001-2015 were included in the study.

INTERVENTION(S)

Physical examination and analysis of blood and semen samples.

MAIN OUTCOME MEASURE(S)

Semen parameters, such as semen volume, sperm concentration, total sperm count, progressively motile sperm count, sperm progressive motility, sperm morphology, and round cells.

RESULT(S)

Many of the semen parameters showed a decreasing trend over the 15-year observation period. The sperm concentration and percentage of sperm with normal morphology decreased from 68 × 10⁶/mL to 47 × 10⁶/mL and from 31.8% to 10.8%, respectively. Although sperm progressive motility showed irregular variation, the progressively motile sperm count decreased from 34 × 10⁶ to 21 × 10⁶ over the 15-year period. Furthermore, the rate of qualified donors fell from 55.78% in 2001 to 17.80% in 2015, and the rate for 2015 was approximately threefold lower than the corresponding rates in 2001.

CONCLUSION(S)

The semen quality among young Chinese men has declined over a period of 15 years, especially in terms of sperm concentration, total sperm count, sperm progressive motility, and normal morphology.

Evaluation of semen quality in 1808 university students, from Wuhan, Central China

The aim of this study was to evaluate the semen quality of university students in Wuhan, the largest city in the world in terms of the number of university students. All student sperm donors recorded in the Hubei Province Human Sperm Bank from 1 March 2010 to 31 December 2013 were screened. At last, a total of 3616 semen samples from 1808 university student sperm donors were eligible and retrospectively analyzed. Each donor's semen parameters were averaged over two samples and compared with the World Health Organization criteria, and a generalized linear regression model was used to examine several determinants of semen quality. We found that the mean and median values were 3.0 ml and 2.8 ml for semen volume, 50.2 × 10⁶ ml⁻¹ and 50.0 × 10⁶ ml⁻¹ for sperm concentration, 148.1 × 10⁶ and 142.1 × 10⁶ for total sperm count, and 58.6% and 60.0% for total sperm motility. About 85.0% of donors had parameters that were all normal. Season and duration of abstinence were critical factors affecting semen quality. We also found a decrease in sperm concentration during the 4 years observation; however, this may not be a strong evidence to confirm the declining trend of semen quality. In conclusion, semen quality of university students in Wuhan was not optimal and should be paid high attention, long-term observation and further study should be carried out to confirm the present situation.