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

Abstract

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. The semen analysis is the most important and the most widely used clinical laboratory test to evaluate male fertility potential. In 2010, the World Health Organization (WHO) criteria had reduced the reference interval of sperm concentration from 20 to 15 million/mL. Concerns about a global decline in semen quality have attracted the attention of researchers and the general public alike. There is an ongoing debate on whether semen quality is declining. In 1992, Carlsen et al 1. reviewed 61 studies and found a worldwide decline trend in semen volume and sperm concentration between 1938 and 1991. After that, several studies have reported a decrease in semen quality in Paris 2 , Tours 3 , Marseille 4 , São Paulo 5 , Shandong 6 , Changsha 7 , and South India 8. In contrast, several other studies have reported no significant change in semen quality in Sydney 9 , Malmö 10 , Montevideo 11 , and Copenhagen 12. These discrepancies could be explained by ethnic, geographical, lifestyle, environmental and between-center variations 13-16. To accurately evaluate changes in semen quality, ethnic, geographical, and between-center variations must be taken into account 15,16. A single-center retrospective investigation of possible changes in semen quality, using the same equipment and based on a large population over a long period of time, has been recommended to minimize these confounding factors 17,18. Based on this, laboratories must conduct their local studies over a certain period of time. Large and long-term population studies on time trends in se...

Spatiotemporal trends in human semen quality

“…By contrast, a study from 2020 that assessed semen data from 23,936 sperm donor candidates at the Henan Sperm Bank of China between 2009 and 2019 did report temporal semen changes 138 . Using multiple linear regression analyses to account for potential confounders (age, BMI, sexual abstinence) suggested that sperm concentration decreased from 62 × 10 6 /ml in 2009 to 32 × 10 6 /ml in 2019 ( P < 0.001), with an average annual rate of 3.9%.…”

“…Overall, the studies with the most relevant design were those that were based on a standardized and controlled assessment of sperm production throughout the study period; relied on a relatively homogeneous group of men throughout the study; covered a sufficiently long period; had a sufficient cross-sectional sample size, in view of the wide distribution of human sperm production; and accounted for the main covariates known to modulate sperm characteristics. In total, and on the basis of these criteria considered together, six studies can be considered to provide relatively robust data on the trends reported: Zorn et al 113 in partners of women with tubal obstruction in Ljubljana (Slovenia), Auger et al 108 among fertile candidates for sperm donation in the Paris area (France) and the studies of Centola et al 87 in Boston (USA), Gyllenborg et al 47 in Copenhagen (Denmark), Shine et al 144 in New Zealand and Liu et al in Henan 138 (China), the latter four studies being carried out among unselected candidates for sperm donation with unknown fertility status (see Supplementary Table 2 ). Five of these six studies reported a decrease in sperm production (sperm concentration and/or sperm count) over time, covering overall the period 1973–2019.…”

“…Finally, the results of a few solid single-centre studies indicating a temporal decline in sperm production 87 , 108 , 113 , 138 , 144 , some of which also show an inverse relationship with year of birth (that is, the youngest men produce the fewest sperm) 87 , 108 , 113 , point to a putative causal role for environmental and lifestyle factors. However, owing to the retrospective nature of the datasets, no major evidence of the possible causal factors has yet emerged from these studies.…”

Are worldwide sperm counts declining?

“…This controversy continues to provoke interest and scientific discussion today, as in the last year four groups published articles examining the question of SCs with two groups finding evidence for decline and two showing no decline (36)(37)(38)(39). The abundance of conflicting data on the topic continues to makes this debate controversial.…”

Relationships of Osmolality and Oxidative Stress with Semen Quality and Their Effects on Male Fertility

“…The study of semen quality is the most important and most commonly used clinical laboratory test to evaluate the capacity of male fertility. In 2010, the World Health Organization (WHO) guidelines lowered the sperm concentration reference interval from 20 million to 15 million/ml [10]. Osmolality is known as a solution's concentration of osmotically active particles.…”