Reviewing reports of semen volume and male aging of last 33 years: From 1980 through 2013

The spermiogram and correlation of seminal fluid parameters in patient attending fertility centre in Lagos, South West Nigeria

BACKGROUND

The determinant of the spermiogram of semen varies in different populations based on several factors ranging, from age to the pathological state of an individual to environmental factors. The aim of the study is to determine the spermiogram of patients that attend fertility clinics in southwest Nigeria and the relationship between the parameters.

METHODOLOGY

This is a cross-sectional study that recruited two hundred and ninety seven (297) patients from two fertility centers in Lagos, Nigeria for the period of January 2021 to November 2022. The sperm samples were collected following WHO standards. The spermiogram was analyzed using an automated sperm analyzer and the descriptive and inference statistics of the study were carried out using R packages (R version 4.2.0).

RESULTS

The result showed the mean age of 43.12±6.95years with median age of 42years. The mean of sperm count and concentration were 114×106 sperm cells and 42×106 per mL with the mean volume of the semen produced by the patients was 2.69mL and average motility (progressive and non-progressive) of the sperm is 47%±19%, 42%±17% has normal morphology. The distributions of the observed variables (seminal fluid parameters) were different from normal distributions in the studied population, such that almost all of them are skewed to the right. The degree of relationship between the sperm parameter were very weak. Nevertheless, specifically, there is a negative correlation between age and sperm count, age and motility, age and volume, and a positive correlation between age and abnormal morphology. The results showed that sperm morphology has a significant effect on motility while sperm morphology significantly depend on sperm count.

CONCLUSION

An increase in sperm volume and concentration improves the sperm morphology and boost the sperm motility, this may increasing the chance of fertility.

Age-Dependent Alterations in Semen Parameters and Human Sperm MicroRNA Profile

The trend to delay parenthood is increasing, impacting fertility and reproductive outcomes. Advanced paternal age (APA), defined as men's age above 40 years at conception, has been linked with testicular impairment, abnormal semen parameters, and poor reproductive and birth outcomes. Recently, the significance of sperm microRNA for fertilization and embryonic development has emerged. This work aimed to investigate the effects of men's age on semen parameters and sperm microRNA profiles. The ejaculates of 333 Portuguese men were collected between 2018 and 2022, analyzed according to WHO guidelines, and a density gradient sperm selection was performed. For microRNA expression analysis, 16 normozoospermic human sperm samples were selected and divided into four age groups: ≤30, 31-35, 36-40, and >40 years. microRNA target genes were retrieved from the miRDB and TargetScan databases and Gene Ontology analysis was performed using the DAVID tool. No significant correlation was found between male age and conventional semen parameters, except for volume. Fifteen differentially expressed microRNAs (DEMs) between groups were identified. Enrichment analysis suggested the involvement of DEMs in the sperm of men with advanced age in critical biological processes like embryonic development, morphogenesis, and male gonad development. Targets of DEMs were involved in signaling pathways previously associated with the ageing process, including cellular senescence, autophagy, insulin, and mTOR pathways. These results suggest that although conventional semen parameters were not affected by men's age, alterations in microRNA regulation may occur and be responsible for poor fertility and reproductive outcomes associated with APA.

An Exploratory Analysis of Firefighter Reproduction through Survey Data and Biomonitoring

Firefighters are occupationally exposed to chemicals that may affect fertility. To investigate this effect, firefighters were recruited to contribute blood, urine, breast milk or semen samples to (1) evaluate chemical concentrations and semen parameters against fertility standards and the general population; (2) assess correlations between chemical concentrations and demographics, fire exposure and reproductive history; and (3) consider how occupational exposures may affect reproduction. A total of 774 firefighters completed the online survey, and 97 firefighters produced 125 urine samples, 113 plasma samples, 46 breast milk samples and 23 semen samples. Blood, urine and breast milk samples were analysed for chemical concentrations (semivolatile organic compounds, volatile organic compounds, metals). Semen samples were analysed for quality (volume, count, motility, morphology). Firefighter semen parameters were below WHO reference values across multiple parameters. Self-reported rates of miscarriage were higher than the general population (22% vs. 12-15%) and in line with prior firefighter studies. Estimated daily intake for infants was above reference values for multiple chemicals in breast milk. More frequent fire incident exposure (more than once per fortnight), longer duration of employment (≥15 years) or not always using a breathing apparatus demonstrated significantly higher concentrations across a range of investigated chemicals. Findings of this study warrant further research surrounding the risk occupational exposure has on reproduction.

Obesity and male infertility: multifaceted reproductive disruption

Background

The global prevalence of obesity has soared to a concerning height in the past few decades. Interestingly, the global decline in semen quality is a parallel occurrence that urges researchers to evaluate if obesity is among the most essential causatives of male infertility or subfertility.

Main body

Obesity may alter the synchronized working of the reproductive-endocrine milieu, mainly the hypothalamic-pituitary-gonadal (HPG) axis along with its crosstalks with other reproductive hormones. Obesity-mediated impairment in semen parameters may include several intermediate factors, which include physical factors, essentially increased scrotal temperature due to heavy adipose tissue deposits, and systemic inflammation and oxidative stress (OS) initiated by various adipose tissue-derived pro-inflammatory mediators. Obesity, via its multifaceted mechanisms, may modulate sperm genetic and epigenetic conformation, which severely disrupt sperm functions. Paternal obesity reportedly has significant adverse effects upon the outcome of assisted reproductive techniques (ARTs) and the overall health of offspring. Given the complexity of the underlying mechanisms and rapid emergence of new evidence-based hypotheses, the concept of obesity-mediated male infertility needs timely updates and pristine understanding.

Conclusions

The present review comprehensively explains the possible obesity-mediated mechanisms, especially via physical factors, OS induction, endocrine modulation, immune alterations, and genetic and epigenetic changes, which may culminate in perturbed spermatogenesis, disrupted sperm DNA integrity, compromised sperm functions, and diminished semen quality, leading to impaired male reproductive functions.

Endocrinopathies and Male Infertility

Male infertility is approaching a concerning prevalence worldwide, and inflicts various impacts on the affected couple. The hormonal assessment is a vital component of male fertility evaluation as endocrine disorders are markedly reversible causatives of male infertility. Precise hormonal regulations are prerequisites to maintain normal male fertility parameters. The core male reproductive event, spermatogenesis, entails adequate testosterone concentration, which is produced via steroidogenesis in the Leydig cells. Physiological levels of both the gonadotropins are needed to achieve normal testicular functions. The hypothalamus-derived gonadotropin-releasing hormone (GnRH) is considered the supreme inducer of the gonadotropins and thereby the subsequent endocrine reproductive events. This hypothalamic–pituitary–gonadal (HPG) axis may be modulated by the thyroidal or adrenal axis and numerous other reproductive and nonreproductive hormones. Disruption of this fine hormonal balance and their crosstalk leads to a spectrum of endocrinopathies, inducing subfertility or infertility in men. This review article will discuss the most essential endocrinopathies associated with male factor infertility to aid precise understanding of the endocrine disruptions-mediated male infertility to encourage further research to reveal the detailed etiology of male infertility and perhaps to develop more customized therapies for endocrinopathy-induced male infertility.

Oxidative Stress, Testicular Inflammatory Pathways, and Male Reproduction

Inflammation is among the core causatives of male infertility. Despite male infertility being a serious global issue, "bits and pieces" of its complex etiopathology still remain missing. During inflammation, levels of proinflammatory mediators in the male reproductive tract are greater than usual. According to epidemiological research, in numerous cases of male infertility, patients suffer from acute or chronic inflammation of the genitourinary tract which typically occurs without symptoms. Inflammatory responses in the male genital system are inextricably linked to oxidative stress (OS). OS is detrimental to male fertility parameters as it causes oxidative damage to reproductive cells and intracellular components. Multifarious male infertility causative factors pave the way for impairing male reproductive functions via the common mechanisms of OS and inflammation, both of which are interlinked pathophysiological processes, and the occurrence of any one of them induces the other. Both processes may be simultaneously found in the pathogenesis of male infertility. Thus, the present article aims to explain the role of inflammation and OS in male infertility in detail, as well as to show the mechanistic pathways that link causative factors of male reproductive tract inflammation, OS induction, and oxidant-sensitive cellular cascades leading to male infertility.

Do lifestyle practices impede male fertility?

Alongside an increasing prevalence of couple and male infertility, evidence suggests there is a global declining trend in male fertility parameters over the past few decades. This may, at least in part, be explained through detrimental lifestyle practices and exposures. These include alcohol and tobacco consumption, use of recreational drugs (e.g., cannabis, opioids and anabolic steroids), poor nutritional habits, obesity and metabolic syndrome, genital heat stress (e.g., radiation exposure through cell phones and laptops, prolonged periods of sitting, tight-fitting underwear and recurrent hot baths or saunas), exposure to endocrine-disrupting chemicals (e.g., pesticide residue, bisphenol A, phthalates and dioxins) and psychological stress. This review discusses these lifestyle practices and the current evidence associated with male infertility. Furthermore, known mechanisms of action are also discussed for each of these. Common mechanisms associated with a reduction in spermatogenesis and/or steroidogenesis due to unfavourable lifestyle practices include inflammation and oxidative stress locally or systemically. It is recommended that relevant lifestyle practices are investigated in clinical history of male infertility cases, particularly in unexplained or idiopathic male infertility. Appropriate modification of detrimental lifestyle practices is further suggested and recommended in the management of male infertility.

The Uruguayan semen donor population: A twenty-eight-year retrospective study

Several studies have reported a global decline in seminal quality over the years. The objective of this study was to describe the semen donor population of Uruguay through comparing data of successive samples banked by the same donors and the analysis of their semen and physical characteristics, ancestry origin and educational level. A total of 3,449 ejaculated samples collected from 71 donors, cryobanked between 1989 and March 2017 at Fertilab, were analysed. Results revealed a mean age of 23.90 ± 3.98 years, an average weight of 74.95 ± 1.09 kg and a mean height of 1.78 ± 0.06 m. The majority of the donors trace their origin to Europe (74.65%, 53/71) and 66.19% (47/71) have a level of education higher than secondary school. We observed longitudinal differences in two parameters, that is sperm concentration and semen volume. Sperm concentration declined, while semen volume increased significantly over the 28-year period. The results of the present study are in accordance with that of previous articles that also reported a decline in sperm concentration over time. However, no differences were observed in total sperm number per ejaculate due to the increase in semen volume values, thus reflecting no real changes in sperm production over time.

Decline in sperm count in European men during the past 50 years

Purpose:

To investigate whether the sperm concentration of European men is deteriorating over the past 50 years of time.

Materials and Methods:

We analysed the data published in English language articles in the past 50 years in altering sperm concentration in European men.

Results:

A time-dependent decline of sperm concentration ( r = −0.307, p = 0.02) in the last 50 years and an overall 32.5% decrease in mean sperm concentration was noted.

Conclusion:

This comprehensive, evidence-based meta-analysis concisely presents the evidence of decreased sperm concentration in European male over the past 50 years to serve the scientific research zone related to male reproductive health.

The Disappearing Sperms: Analysis of Reports Published Between 1980 and 2015

Reports regarding the changes in sperm concentration in different counties of the world are inconsistent. Furthermore, the reports that sprung up from specific epidemiological and experimental examinations did not include data of prior studies or geographical variations. The current study, following a previous report of massive fall in semen volume over the past 33 years, attempts to delineate the trend of altering sperm concentrations and factors responsible for this by reviewing article published from 1980 to July 2015 with geographic differences. The current study identified an overall 57% diminution in mean sperm concentration over the past 35 years ( r = -.313, p = .0002), which, when analyzed for each geographical region, identified a significant decline in North America, Europe, Asia, and Africa. An increasing trend of sperm concentration was identified only in Australia. The association of male age with such a trend ( R² = .979) is reported. The authors also correlated male fertility with sperm concentration. Thus, this comprehensive, evidence-based literature review aims to concisely and systematically present the available data on sperm concentration from 1980 to 2015, as well as to statistically analyze the same and correlate male health with the declining pattern of sperm count in a single scientific review to serve the scientific research zone related to reproductive health. It points to the threat of male infertility in times ahead.