Circannual rhythm in human sperm count revealed by serially independent sampling

Sperm concentration remains stable among fertile American men: a systematic review and meta-analysis

IMPORTANCE

Findings from several high profile meta-analyses have raised concerns about an ongoing global decline in sperm concentration and male fertility. However, these studies exhibit considerable heterogeneity in key variables including study population, methodology, fertility status, and geographic region.

OBJECTIVE

To perform a systematic review and meta-analysis exploring temporal trends in sperm concentration among fertile men and men unselected for fertility status in the United States.

DATA SOURCES

A literature search performed in Scopus and PubMed databases for studies published between 1970 and 2023. Additional studies were included from citations of prior global meta-analyses and reviews evaluating temporal trends in sperm count.

STUDY SELECTION AND SYNTHESIS

Studies were included if they presented original data on sperm concentration in US men without known infertility from 1970 to 2023. Aggregate data were assessed across all study populations, with additional subgroup analyses stratified by fertility status and US region.

MAIN OUTCOMES

Weighted generalized linear models were generated to evaluate the association between mean sperm concentration and sample collection year.

RESULTS

A total of 874 articles were screened, with 58 meeting the inclusion criteria. These represented 75 unique study populations totaling 11,787 men in the United States. Across all study populations, no change in sperm concentration was observed between 1970 and 2018 in unadjusted models (β = 0.14 million/mL per year). When adjusting for US region, no statistically significant decline in sperm concentration was seen. When adjusting for both region and fertility status, a modest annual decline was observed to meet statistical significance (β = -0.35 million/mL per year). Of the 49 study populations reporting adequate data to determine mean total sperm count, there was a significant increase in total sperm count of 2.9 million per year between 1970 and 2018. Subgroup analysis found no statistically significant change in mean sperm concentration among any US census region or fertility status cohort.

CONCLUSION AND RELEVANCE

In contrast to prior global studies, this analysis suggests no clinically significant decline in sperm concentration among confirmed fertile men and the general male US population without known infertility. Although these findings provide some reassurance against a widespread rapid decline, further studies are necessary to better understand this important topic.

Characteristics of Ultrasound and Magnetic Resonance Imaging of Normal Testes and Epididymis Besides Angiography of Testicular Artery in Dromedary Camel

Decreasing male fertility encouraged the investigators to innovate accurate diagnostic non-invasive methods for detection of changes in the testicular parenchyma. Ultrasonography (US) has the potential to be used in this manner for decades, but magnetic resonance imaging (MRI) is still of limited application in animals for this purpose. The current study was designed to describe appearances and quantitative MRI attributes of the normal testes, epididymis besides angiography of testicular artery in camels. About 30 apparently healthy male dromedary camels aged 8–14 years were slaughtered during the rutting season. Immediately after slaughtering, the male gonads (n = 30 pairs of testicles and epididymis) were subjected to morphometric evaluation using a Vernier caliper and ultrasound scanning. Epididymial sperms were evaluated for motility, vitality and abnormality. MRI was performed for testes (n=16) by using a 1.5T Excite-II MRI apparatus of Sigma. Radiography and angioarchitecture of testicular artery (n=24) were done. Camel testicular length, width, and depth showed non-significant differences between a Vernier caliper or sonar. The MRI results revealed that both the testis and epididymis have homogenously intermediate signal (T1) and testes have hyperintense signal, with slightly lower signal in the epididymis (T2). In conclusion, both the ultrasonography and MRI techniques, with each respective computer-assisted imaging, could be used to detect the histomorphological changes of the camels' testicles. However, US imaging remains the first diagnostic technique for evaluating the reproductive health in men for its lower cost and accuracy. MRI is beneficial when the sonograms are inconclusive and/or equivocal. It shows the examined tissues in greater anatomical details compared to ultrasonography. Further studies are needed to compare between characteristics of US and MRI of normal testes and epididymis with testicular artery angiography in living camel during rut season and non-rut season and between normal healthy and affected diseased genitalia.

Heat stress response of somatic cells in the testis

The testis is a temperature-sensitive organ that needs to be maintained 2-7 °C below core body temperature to ensure the production of normal sperm. Failure to maintain testicular temperature in mammals impairs spermatogenesis and leads to low sperm counts, poor sperm motility and abnormal sperm morphology in the ejaculate. This review discusses the recent knowledge on the response of testicular somatic cells to heat stress and, specifically, regarding the relevant contributions of heat, germ cell depletion and inflammatory reactions on the functions of Sertoli and Leydig cells. It also outlines mechanisms of testicular thermoregulation, as well as the thermogenic factors that impact testicular function.

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.

The Association Between Testis Cancer and Semen Abnormalities Before Orchiectomy: A Systematic Review

Purpose: Testicular germ cell tumors (TGCT) are the most common solid organ malignancy in young men. It is a largely curable disease, so the extent to which it affects quality of life-including male fertility-is important. Abnormal semen analysis is highly predictive of male infertility. We conducted a systematic review of published studies that reported pre-orchiectomy semen parameters (as a surrogate for fertility) in TGCT patients to evaluate the association between TGCT and semen abnormalities before orchiectomy. Methods: We conducted a systematic review of peer-reviewed publications reporting semen parameters before orchiectomy in adult patients diagnosed with TGCT. Further, we assessed the association between TGCT and semen abnormalities that may lead to infertility. Results: We applied MeSH search terms to four online databases (PubMed, Cochrane Reviews, Web of Science, and Ovid), resulting in 701 potentially relevant citations. After conducting a three-stage screening process, six articles were included in the systematic review. For each study, the participants' data and the study's quality and risk of bias were assessed and described. All studies showed semen abnormalities-including count, motility, and morphology-in men with TGCT prior to orchiectomy. Conclusions: TGCT is associated with semen abnormalities before orchiectomy. This review shows an increase in abnormal semen parameters among men with TGCT even outside the treatment effects of orchiectomy, radiation, or chemotherapy. To improve long-term quality of life, these findings should be considered when counseling patients on future fertility and sperm banking during discussions about treatment and prognosis for TGCT.

Causes, effects and molecular mechanisms of testicular heat stress

The process of spermatogenesis is temperature-dependent and occurs optimally at temperatures slightly lower than that of the body. Adequate thermoregulation is imperative to maintain testicular temperatures at levels lower than that of the body core. Raised testicular temperature has a detrimental effect on mammalian spermatogenesis and the resultant spermatozoa. Therefore, thermoregulatory failure leading to heat stress can compromise sperm quality and increase the risk of infertility. In this paper, several different types of external and internal factors that may contribute towards testicular heat stress are reviewed. The effects of heat stress on the process of spermatogenesis, the resultant epididymal spermatozoa and on germ cells, and the consequent changes in the testis are elaborated upon. We also discuss the molecular response of germ cells to heat exposure and the possible mechanisms involved in heat-induced germ cell damage, including apoptosis, DNA damage and autophagy. Further, the intrinsic and extrinsic pathways that are involved in the intricate mechanism of germ cell apoptosis are explained. Ultimately, these complex mechanisms of apoptosis lead to germ cell death.

Decreasing sperm quality: a global problem?

BACKGROUND

Carlsen and coworkers (1992) reviewed 61 heterogeneous observational studies on semen quality published between 1938 and 1990. This review indicates that mean sperm density decreased significantly between 1940 and 1990. An extended meta-analysis with 101 studies confirmed a decline in sperm density for the period from 1934 to 1996 (2000). The key message of the meta-analyses is that sperm counts have decreased globally by about 50% over the past decades. This assessment has been questioned.

DISCUSSION

A major methodological problem of the meta-analysis is the use of data collected in different countries, at different times, on different populations and with different methods of semen analysis. Furthermore, the results of studies concerning semen analysis are frequently biased e.g. by selection criteria of volunteers. In most studies on human semen characteristics the populations under study are insufficiently defined and the study participants are not a representative population sample. The incidence of testicular cancer has increased in Caucasian men worldwide. The investigation of common risk factors for male reproductive disorders requires well designed epidemiological studies and the collection of individual data.

SUMMARY

Former meta-analyses of sperm count data show a global downward trend. This conclusion should be interpreted with caution. The included studies are of great heterogeneity due to geographical and/or ethnical variation, different study designs and different methodological standards. Population-based prospective studies are needed to investigate secular trends in male reproductive disorders.

Temporal trends in bull semen quality: a comparative model for human health?

INTRODUCTION

A decline in human semen quality over the past 30-60 years has been reported in numerous epidemiological studies from the United States and Europe. We evaluated temporal trends in semen quality parameters in dairy bulls. The long-term management of dairy bulls for artificial insemination presented a unique opportunity to evaluate temporal trends in semen quality and explore this relationship as a potential animal model for reproductive abnormalities in humans.

MATERIALS AND METHODS

Bull semen analysis data from 1965 through 1995 were collected from a large artificial insemination organization. Semen analyses from 12- to 18-month-old Holstein dairy bulls were included in the study and consisted of daily sperm concentration, daily ejaculate volume, total daily sperm output, percentage of sperm with normal morphology, and percentage of sperm with normal post-thaw motility. Multiple regression analysis, logistic regression, and general linear modeling were used to determine temporal trends over the 30-year period.

RESULTS AND DISCUSSION

Semen quality appears to have declined from 1970 to 1980 or 1985 as manifested by declines in daily ejaculate volume, daily sperm concentration, and total daily sperm output. In contrast, sperm morphology and motility improved over the same period. In approximately 1980 or 1985, depending on the parameter, ejaculate volume, sperm concentration, total sperm, and motility improved. However, normal morphology began to deteriorate during this same period. Methodological inconsistencies over time introduce uncertainty in analyses of temporal trends in semen quality in this and previous human studies. However, changes in technology do not appear to be solely responsible for the temporal trends observed. The source of the decline in semen quality in the bulls studied is unknown. If the decline in semen quality were due to exposure to endocrine disrupting chemicals, then a continued decline or a leveling-off would be expected. Instead, a rise in semen quality was observed during the latter portion of the observation period.

Human exposure to endocrine disrupters and semen quality

Reproductive pathology in the male represents about 20% of infertility cases. Male infertility may be attributed to a number of causes, including genetic and congenital abnormalities, infection, multisystemic diseases, varicocele, and others; however, a significant number of cases are idiopathic. Global declines in semen quality were suggested to be associated with enhanced exposure to environmental chemicals that act as endocrine disrupters as a result of our increased use of pesticides, plastics, and other anthropogenic materials. A significant body of toxicology data based upon laboratory and wildlife animals studies suggests that exposure to certain endocrine disrupters is associated with reproductive toxicity, including (1) abnormalities of the male reproductive tract (cryptorchidism, hypospadias), (2) reduced semen quality, and (3) impaired fertility in the adult. There is, however, a relative paucity of studies designed to measure exposure to endocrine disrupters on semen quality parameters (sperm concentration, motility, morphology). An overview of the human semen quality literature is presented that examines the role of endocrine disrupters including organochlorines (OC), dioxins, phthalates, phytoestrogens, and chemical mixtures (pesticides and tobacco smoke).

Decline and loss of birth seasonality in Spain: analysis of 33,421,731 births over 60 years

BACKGROUND AND AIM

Several seasonal variations have been found in birth rates in different countries at different periods. The characteristics of the rhythmic patterns vary according to geographical location and chronological changes. This study presents data on spanish birth seasonality over six decades.

METHODS

A time series composed of 33,421,731 births in Spain in the period 1941-2000 was analysed. The series comes from the National Institute of Statistics and was processed according to the following norms: (1) normalisation of the duration of months and years; (2) clinical analysis of temporal series (isolation of seasonal component); (3) Fourier's spectral analysis; and (4) cosinor analysis (adjustment to the cosine curve of two harmonics).

RESULTS

Significant seasonal rhythm was found in the set of births, both for a 12-month period and a 6-month period. The rhythm shows bimodal morphology, with a pronounced birth peak in April and a smaller one in September. These peaks correspond to July and December conceptions, respectively. The major birth peak shifted to March-May between the 1940s and the 1980s. Birth rhythm changed after the 1960s, with a decrease in amplitude and later loss of seasonality in the 1990s.

CONCLUSIONS

In Spain, seasonal birth rhythm shows a decline from 1970, and, finally, lack of birth seasonality in 1991-2000. This trend is similar to other European countries, although Spain shows a more intense loss of seasonality.

Within-subject variation of seminal parameters in men with infertile marriages

As little information exists on the semen variability in infertile men, this study aimed at analysing the within-subject variability of semen from men with infertile marriages included in an intrauterine insemination (IUI) programme. Five ejaculates from each of 436 men (2180 specimens) were analysed. The within-subject coefficients of variation (CV(w)) were high for all parameters (semen volume, sperm concentration, forward motility and combined parameters), ranging from 0.73 for the total motile sperm count to 0.27 for the semen volume. Nevertheless, within-subject fluctuations were smaller than the between-subject variability, as indicated by high Intraclass Correlation Coefficient (ICC) values, which, however, significantly lowered when <or=3 samples were analysed against five samples. Neither seasonality nor the length of abstinence between 3 and 7 days significantly affected within-subject semen variability, whereas total motile sperm count was significantly and negatively affected at 2 days of abstinence. In 253 cycles of double IUI, performed in two consecutive days, semen volume and parameters including volume decreased in the second sample, but semen quality improved in most cases of oligo- and/or asthenozoospermia. Useful information for clinical purposes is provided.

Semen quality of 324 fertile Japanese men

BACKGROUND

A number of studies have indicated regional differences in semen quality. To examine the current status in Japan, we undertook a cross-sectional study on the semen quality of fertile Japanese men for comparison with recent European results.

METHODS

Semen parameters of 324 fertile men from the Kawasaki/Yokohama area were investigated. The semen parameters were compared with those published for fertile men from four European cities, Copenhagen, Paris, Edinburgh and Turku.

RESULTS

When adjusting for confounders such as ejaculation abstinence period and age, the lowest sperm concentrations were detected in men from Kawasaki/Yokohama followed by men from Copenhagen, Paris, Edinburgh and Turku, but only the differences between men from Kawasaki/Yokohama and men from Edinburgh and Turku were significant (P=0.0008 and P<0.0001, respectively). Total sperm count, percentage of motile sperm and percentage of normal sperm observed in Kawasaki/Yokohama were significantly lower than those from all European centres except for motile sperm in men from Paris.

CONCLUSIONS

Japanese fertile men had a semen quality at the level of Danish men, who have been reported to have the lowest among investigated men in Europe. The low level of semen quality of the fertile Japanese men may be due to lifestyle or other environmental factors; however, ethnic differences caused by different genetic variation or combinations cannot be ruled out by this study.

Lack of seasonal variations in fertilization, pregnancy and implantation rates in women undergoing IVF

BACKGROUND

Several studies have investigated seasonal variations during IVF. Their results are contradictory, especially concerning fertilization and pregnancy rates. The aim of the present study was to re-evaluate these parameters using a large number of IVF cycles.

METHODS

A total of 7368 IVF cycles conducted in Switzerland between 1995 and 2003 were retrospectively analysed. To avoid a bias in the evaluation of the fertilization rate, only IVF cycles without ICSI were considered for analysis. Cycles were assigned to seasons according to the date of the beginning of stimulation.

RESULTS

There were no statistically significant differences between the seasons concerning the fertilization, the pregnancy and the implantation rates. However, statistically significant variables deciding on the outcome of an IVF cycle are age, centre, aetiology of infertility and day of transfer.

CONCLUSIONS

There were no statistically significant seasonal differences in central Europe (Switzerland) that influenced the outcome of IVF treatment. The only statistically significant variables of IVF outcome were age, centre, aetiology of infertility and day of transfer. A change to routine fertility treatment concerning the different seasons should therefore not be taken into account.

Cryptorchidism: an indicator of testicular dysgenesis?

Cryptorchidism is a common ailment of new-born boys, affecting 1-9% of full term boys at birth. Cryptorchidism has been associated with an increased risk of testicular cancer and reduced fertility. Aetiology of cryptorchidism remains obscure in most cases. Familial occurrence suggests a heritable susceptibility to cryptorchidism; however, seasonal variation in the incidence of cryptorchidism suggests that environmental factors also contribute. Testicular descent is characterised by androgen-dependent regression of cranial suspensory ligament and androgen + insulin-like hormone 3 (Ins l3)-dependent gubernacular outgrowth. Even though hormonal defects are rarely detected in patients, both hypo-and hypergonadotropic hormonal patterns have been associated with cryptorchidism. Moreover, cryptorchid boys have significantly reduced serum androgen bioactivity at 3 months of age when normal boys have a strong surge of reproductive hormones. Defects in Ins l3 action cause cryptorchidism in male mice, and over-expression in female mice causes ovarian descent. Defects in leucine-rich repeat-containing G-protein-coupled receptor 8/G-protein-coupled receptor affecting testis descent (LGR8/GREAT), the receptor for Ins l3, manifest the same phenotype as Ins l3 knockout mutants. Even though mutations found in Ins l3 and LGR8/GREAT genes are not a common cause of cryptorchidism in patients, it remains to be resolved whether low Ins l3 levels during development are associated with cryptorchidism. Cryptorchidism may reflect foetal testicular dysgenesis that may later manifest as subfertility or testicular cancer.

Circannual rhythm in the incidence of cryptorchidism in Finland

Conflicting data on circannual variation in birth rates of urogenital malformations have been reported previously. To assess risk factors of cryptorchidism we studied the seasonal variation of cryptorchidism in Finland. We performed a prospective cryptorchidism study in Turku, Finland, from 1997 to 2001 to evaluate the incidence of cryptorchidism. Clinical examinations were performed at birth and at 3 months. Of 9511 liveborn boys (1471 preterm boys) 216 (53 preterm boys) were cryptorchid at birth and 106 (19 preterm boys) at 3 months. The incidence of cryptorchidism was significantly higher in spring (February-April) (3.0%) than in summer (May-July) (1.7%) (OR 1.79; 95% CI: 1.23-2.63). This seasonal difference was observed both among preterm and term boys. We conclude that a circannual fluctuation in the incidence of cryptorchidism exists, which indicates an influence by environmental factors. The underlying reason for cyclicity affects similarly both preterm and term boys.

Longitudinal changes in semen parameters in young Danish men from the Copenhagen area

BACKGROUND

Several recent studies have reported low sperm concentration in young men recruited from the general population, but it is unknown whether the semen quality of these young men reflects that of more mature men or is reduced due to relative immaturity. We conducted a longitudinal follow-up study to address this question.

METHODS

We followed 158 young men (median age = 19.1 years at entry) for up to 4 years and requested quarterly semen samples (total 1838 semen samples) and yearly genital examinations. We examined longitudinal changes in sperm concentration, semen volume, percentage of immotile sperm and percentage of morphologically normal sperm. We used general linear models in which each man served as his own control which also controlled for age, smoking, urogenital infections or disorders, fever and abstinence time.

RESULTS

We found no evidence that sperm concentration, total sperm count or percentage of morphologically normal sperm changed appreciably during the 4 years of follow-up. Semen volume appeared to increase slightly with age, perhaps due to greater acceptance of the study protocol by participants. Sperm motility also improved somewhat, although this may, at least in part, reflect a trend in motility measurement.

CONCLUSIONS

In this analysis of 1838 semen samples from 158 young men from the Copenhagen area, sperm concentration, total sperm count and sperm morphology did not change significantly during 4 years of follow-up, suggesting that previously reported low sperm concentration and poor sperm morphology among young Danish men are unlikely to be the result of immaturity.

Comparison of sperm counts in two groups of men presenting for infertility investigations 20 years apart

Aims:  To compare sperm counts for two groups of men who had presented for infertility investigations approximately 20 years apart. Methods:  The study compared results for 309 men tested between 1977 and 1981 with those of 559 men tested between 1997 and 1998 using identical methodology. In order to approximate the normal population, only those men with counts above 5 million/mL were included in the final analysis. Bias, due to repeated testing after an initial abnormal result, was minimized by including only the patient's first test results. In addition, to allow for time-dependent changes in the requirements for semen samples, results were included only if a complete sample was produced by masturbation after 3-5 days abstinence. Results:  There was a small, but statistically significant drop in ejaculate volume (3.9-3.6 mL, P = 0.015) and a significant increase in the patient's mean age (32.18 vs 35.08, P < 0.001). Both groups had median abstinence of 3 days and no difference in sperm counts with a mean (median) count for the early group of 87.9 (75) versus 92.0 (76) for the recent group (P > 0.80). The significant drop in ejaculate volume was not reflected in a difference (P = 0.45) in total sperm numbers in the ejaculate with 320.7 (255) versus 313.1 (234). Conclusion:  This study found no evidence of a decrease in sperm counts or total sperm output in men (excluding those with severe oligospermia) presenting for infertility investigations in Melbourne, Australia, over the last two decades of the twentieth century. (Reprod Med Biol 2004; 3: 211-216).

Reproductive function during summer and winter in Norwegian men living north and south of the Arctic circle

Seasonal, daylight-dependent variation in human spermatozoa counts, with lowest values during summer, has been suggested. To test this hypothesis, we performed a longitudinal study of semen quality and reproductive hormone levels in Norwegian men living north and south of the Arctic Circle. An ejaculate and a serum specimen were obtained both in summer and in winter from 92 volunteers in Tromsoe (69 degrees north latitude) and 112 in Oslo (60 degrees north latitude). Semen analyses were performed, and serum was assayed for FSH and inhibin B. The median spermatozoa concentration in Tromsoe after adjustment for abstinence period length was 49 x 10(6)/ml in summer and 54 x 10(6)/ml in winter. Corresponding values for Oslo were 59 x 10(6)/ml and 54 x 10(6)/ml. The seasonal differences in spermatozoa concentration were not statistically significant, nor were significant differences observed in median total spermatozoa count, semen volume, percentage progressive motile spermatozoa, or FSH. In Tromsoe, but not Oslo, inhibin B concentration was slightly, but significantly (P = 0.02) higher in winter than summer (229 ng/liter vs. 223 ng/liter). The length of the daylight period may have a slight impact on hormonal markers of spermatogenesis but does not cause substantial changes in spermatozoa numbers and motility.

Effects of ejaculatory frequency and season on variations in semen quality

OBJECTIVE

To describe the intraindividual variation in semen parameters.

DESIGN

Prospective, longitudinal study.

SETTING

Academic research environment.

PATIENT(S)

Twenty-seven healthy men, followed monthly for 16 months.

INTERVENTION(S)

Monthly semen samples were collected, as well as information regarding duration of abstinence, febrile episodes, and ejaculatory frequency.

MAIN OUTCOME MEASURE(S)

Sperm concentration, percentage immotile spermatozoa, and percentage morphologically normal spermatozoa.

RESULT(S)

There were no significant seasonal variations in sperm concentration, motility, or morphology. The ejaculatory frequency was significantly higher during spring compared with winter months. There was a significant difference in sperm concentration with respect to having one, two, or more than two ejaculations during a 7-day period before the abstinence period. Sperm motility and morphology were not affected by ejaculatory frequency. Duration of abstinence, ejaculatory frequency, and fever accounted only little for the high intraindividual variation in individual semen parameters. Three semen samples compared with two reduced the intraindividual variations as follows: sperm concentration from 41% to 33.5%, percentage normal spermatozoa from 6.9% to 5.7%, and percentage immotile spermatozoa from 19% to 15.5%.

CONCLUSION(S)

Ejaculatory frequency but not season significantly affected sperm concentration. Most of the intraindividual variations in semen parameters could not be explained by duration of abstinence, fever, or ejaculatory frequency.

Quality control, quality assurance, and proficiency testing in the andrology laboratory

The primary goal of any andrology laboratory should be the performance of accurate, reproducible, high-quality, and clinically relevant laboratory testing. An underlining objective of such a goal is to better serve the ordering physician, and the patient, by continually improving laboratory performance. Quality control (QC) is the procedure that determines accurate and reproducible testing. Proficiency testing (PT) is the process allowing physicians to compare results from one laboratory to another. Quality assurance (QA) is the mechanism ensuring high-quality, clinically relevant testing. Together, QC, QA, and PT serve as the foundation responsible for a program that continually improves the overall quality of the testing, allowing the physician ordering the test to be more effective in treating the patient. Several examples are presented to assist the implementation of effective QC and QA programs aimed at continually improving performance in the andrology laboratory.

Circannual variation in human semen parameters

The aim of the present study was to determine whether there were significant monthly variations in the semen parameters (i.e. volume, sperm count, total sperm count, motile and normal sperm count) of men living in a Mediterranean climate area. A total of 10 877 semen analysis results were included. Semen samples were obtained as a part of an initial screening of male partners from couples with infertility problems who were attending our laboratory from 1970 to 2000. Log transformation and cubic root transformation were used to test the sample distribution. Statistical significance was adjusted by year of examination, patient's age and sexual abstinence period by performing covariance analyses. Differences between months were assessed with the Bonferroni post-hoc test. There was an increase in March and a decrease in September in the adjusted mean sperm count (p < 0.0005), total sperm count (p < 0.0005), motile sperm count (p=0.01) and normal sperm count (p=0.002). There were no variations in semen volume in the study period. Monthly changes in semen quality are confirmed in this population.

Seasonal changes in human sperm chromatin condensation

PURPOSE

The aim of this study was to investigate possible seasonal changes in human sperm parameters, especially chromatin condensation.

METHOD

In a first run, 3155 patients attending the andrological outpatient clinic at the Centre of Dermatology and Andrology at Justus Liebig University, Giessen, Germany, from January 1992 to October 1995 were examined for sperm count, motility, vitality, and chromatin condensation.

RESULTS

The respective results were correlated according to season. Significant seasonal changes were observed in chromatin condensation and sperm count, with mean maximum values (for chromatin condensation and sperm count) of 86.24% aniline blue-negative spermatozoa in January and 68.75 x 10(6) mL-1 in April. To confirm the observation of seasonal changes in sperm chromatin condensation in Germany on the Southern Hemisphere, 179 patients attending the Reproductive Biology Unit at Tygerberg Hospital, Tygerberg, South Africa, were examined by means of the aniline blue stain from April 1999 to April 2000. For chromatin condensation, a significant seasonal change shifted by 4-5 months was observed on the Southern Hemisphere. However, no seasonal variations could be found for the sperm count.

CONCLUSIONS

Our results clearly demonstrate seasonal changes in sperm count and chromatin condensation. In contrast, no circannual relation was observed for motility and vitality.

Regional differences in semen quality in Europe

Recent reports have indicated a decrease in semen quality of men in some countries, and suggested regional differences. A study was undertaken of semen samples from 1082 fertile men from four European cities (Copenhagen, Denmark; Paris, France; Edinburgh, Scotland; and Turku, Finland). Semen analysis was standardized, inter-laboratory differences in assessment of sperm concentration were evaluated, and morphology assessment centralized. Lowest sperm concentrations and total counts were detected for Danish men, followed by French and Scottish men. Finnish men had the highest sperm counts. Men from Edinburgh had the highest proportion of motile spermatozoa, followed by men from Turku, Copenhagen and Paris. Only the differences between Paris/Edinburgh and Paris/Turku were statistically significant (P < 0.003 and P < 0.002 respectively). No significant differences in morphology were detected. A general seasonal variation in sperm concentration (summer 70% of winter) and total sperm count (summer 72% of winter) was detected. Semen quality of a 'standardized' man (30 years old, fertile, ejaculation abstinence of 96 h) were estimated. Typically, sperm concentrations (x 10(6)/ml) for winter/summer were: Turku 132/93; Edinburgh 119/84; Paris 103/73; and Copenhagen 98/69. These differences in semen quality may indicate different environmental exposures or lifestyle changes in the four populations. However, it remains to be seen whether such changes can account for these differences. These data may also serve as a reference point for future studies on time trends in semen quality in Europe.

Semen quality and reproductive hormones before orchiectomy in men with testicular cancer

PURPOSE

To obtain information about preorchiectomy gonadal function in patients with testicular germ cell cancer to improve the clinical management of fertility and other andrologic aspects in these men.

PATIENTS AND METHODS

In group 1, a group of 83 consecutive patients with testicular germ cell cancer (TGCC) investigated before orchiectomy, semen analysis was carried out in 63 patients and hormonal investigations, including measurement of follicle-stimulating hormone, luteinizing hormone (LH), testosterone, estradiol, sex hormone-binding globulin (SHBG), inhibin B, and human chorionic gonadotropin (hCG), in 71 patients. Hormone levels in patients with elevated hCG (n = 41) were analyzed separately. To discriminate between general cancer effects and specific effects associated with TGCC, the same analyses were carried out in a group of 45 consecutive male patients with malignant lymphoma (group 2). Group 3 comprised 141 men employed in a Danish company who served as controls in the comparison of semen parameters. As a control group in hormone investigations, 193 men were selected randomly from the Danish National Personal Register to make up group 4.

RESULTS

We found significantly lower sperm concentration (median, 15 x 10(6)/mL; range, 0 to 128 x 10(6)/mL) and total sperm count (median, 29 x 10(6)/mL; range, 0 to 589 x 10(6)) in patients with testicular cancer than in patients with malignant lymphomas (sperm concentration: median, 48 x 10(6)/mL; range, 0.04 to 250 x 10(6)/mL; sperm count: median, 146 x 10(6); range, 0.05 to 418 x 10(6)) (P < .001 and P < .001) and healthy men (sperm concentration: median, 48 x 10(6)/mL; range, 0 to 402 x 10(6)/mL; sperm count: median, 162 x 10(6); range, 0 to 1253 x 10(6)) (P < .001 and P < .001). FSH levels were increased in men with testicular cancer (median, 5.7 IU/L; range, 2.0 to 27 IU/L) compared with both men with malignant lymphomas (median, 3.3 IU/L; range, 1.01 to 12.0 IU/L) and healthy controls (median, 4.1 IU/L; range, 1.04 to 21 IU/L)(P = .001 and P = .007, respectively). Surprisingly, we found significantly lower LH in the group of men with TGCC (median, 3.6 IU/L; range, 1.12 to 11.9 IU/L) than in healthy men (median, 4.7 IU/L; range, 1.3 to 11.9 IU/L) (P = .01). We could not detect any differences between men with testicular cancer and men with malignant lymphomas and healthy men with regard to serum levels of testosterone, SHBG, and estradiol. Men with testicular cancer who had increased hCG levels had significantly lower LH and significantly higher testosterone and estradiol than those without detectable hCG levels.

CONCLUSION

Spermatogenesis is already impaired in men with testicular cancer before orchiectomy. Neither local suppression of spermatogenesis by tumor pressure nor a general cancer effect seems to fully explain this impairment. The most likely explanation is preexisting impairment of spermatogenesis in the contralateral testis in men with testicular cancer. The question of whether also a pre-existing Leydig cell dysfunction is present in men with testicular cancer could not be answered in this study because the tumor seems to have a direct effect on the Leydig cells. Men with testicular cancer had low LH values as compared with controls. We speculate that increased intratesticular level of hCG also in men without measurable serum hCG may play a role by exerting LH-like effects on the Leydig cells, causing increased testosterone and estrogen levels and low LH values in the blood.

Secular and seasonal changes in semen quality among young Danish men: a statistical analysis of semen samples from 1927 donor candidates during 1977-1995

The objective of this study was to investigate whether semen quality has changed during the years 1977-1995 in a group of unselected semen donor candidates, and to determine whether semen quality is subject to seasonal variation, by analysis of time- and season-related changes in semen quality using multiple regression and ANOVA. The study was based on analysis of the first semen sample delivered by 1927 semen donor candidates in Copenhagen during the period 1977-1995, with determination of semen volume, sperm concentration, total sperm count, percentage motile spermatozoa, and a semiquantitative sperm motility score. Multiple linear regression analysis with year, sexual abstinence and season as covariates showed a significant increase in mean sperm concentration from 53.0 x 10(6)/mL in 1977 to 72.7 x 10(6)/mL in 1995 (p < 0.0001) and in mean total sperm count from 166.0 x 10(6) to 227.6 x 10(6) (p < 0.0001). Mean semen volume and percentage motile spermatozoa did not change. Sperm motility deteriorated, as the spermatozoa in 74.2% of the samples were of excellent motility in 1977-1980 compared to only 41.9% in 1993-1995 (chi 2 = 130.0, p < 0.0001). Analysis of variance showed significant variation between seasons regarding sperm concentration (p < 0.0001) and total sperm count (p < 0.0001). Highest sperm counts were found in spring, with a mean concentration (95% C.I.) of 77.6 x 10(6)/mL (71.9-83.7), and lowest in summer, with a mean of 57.5 x 10(6)/mL (50.1-65.4). No other semen parameter varied with season. It is concluded that sperm counts increased, whereas sperm motility decreased, in a group of Danish semen donor candidates, from 1977 to 1995. Due to the retrospective design and the anonymity of the donors, we were unable to control for variation in donor age, and we cannot exclude the possibility that some donor candidates were selected by being accepted as donors by other semen donor services in Copenhagen. With these limitations in mind, we suggest our results should be interpreted cautiously and regarded as a contribution to the ongoing dispute on whether or not there is a continuous decrease in sperm quality. The seasonal variations found in sperm concentration and total sperm count were pronounced and were not attributable to seasonal differences in the length of sexual abstinence. Additionally, the same seasonal pattern was observed in five successive year-intervals. These findings strongly indicate that human testicular function is influenced by season, a phenomenon well known in many lower mammals.

Reproductive exocrine and endocrine profiles and their seasonality in male langur monkeys (Presbytis entellus entellus)

The reproductive exocrine and endocrine profiles in male langurs are reported with an emphasis on seasonality. The animals showed positive response to electroejaculation throughout the year. The sperm concentration varied between 10-383 x 10(6)/ejaculation with wide fluctuations all through the year. No appreciable changes in the motility and percent live sperm were observed throughout the year. The levels of seminal fructose and magnesium remained unchanged throughout the year, while acid phosphatase showed wide fluctuations. Citric acid showed elevation during February and March and LDH showed elevated levels during April and May. The annual range of serum testosterone was 6-34 nMol/l with a peak during July. Cortisol ranged between 575-1587 nMol/l and prolactin ranged between 107-900 mU/l. Wide fluctuations were observed in hormonal levels. No seasonality was exhibited in the seminiferous tubule diameter, nuclear diameter of Sertoli cells and Leydig cells, and the cholesterol, glycogen, and sialic acid contents of testis. None of the parameters studied have shown any correlation with season. The results suggest that the male langurs lack seasonality in their reproductive exocrine and endocrine profiles and thus could be used as model for research in human reproduction.

Worldwide variations in sperm counts

OBJECTIVES

Based on the premise that various human disease processes manifest differently depending on geography, we set out to determine whether sperm counts vary from different nations and different regions within the United States.

METHODS

We reviewed the literature of all significant population-based studies that evaluated sperm counts from fertile or presumably fertile men from 1930 to the present.

RESULTS

We found that sperm counts did, in fact, vary greatly. Throughout the United States, average sperm counts ranged from a low of 48 million/cc in lowa to a high of 134 million/cc in New York, with multiple values in-between from Texas, Minnesota, Washington State, and California. Internationally, average sperm counts ranged from a low of 52.9 million/cc in Thailand to a high of 102.9 million/cc in France.

CONCLUSIONS

We conclude that sperm counts are subject to a wide range of variation among geographic locations.

Chronobiological fluctuations in semen parameters with a constant abstinence period

This study examined the seasonal variation in three semen parameters (total sperm count, % grade a progressive motility and sperm morphology according to strict criteria) with an identical abstinence period of 24 h. A total of 340 spermiograms of 107 different men enrolled in an intrauterine insemination (IUI) program were examined. To reduce variation due to interindividual disparities in semen quality, differences of each test result from the mean value obtained for that individual were analyzed. Mean values resulted from at least 3 observations during different IUI cycles. Using ANOVA and spectral analysis, no differences in semen parameter results in function of the month of the year were observed. The lack of any significant periodicity may be explained by the large biological variation for individual semen parameters and/or the lack of significant differences regarding light exposure and temperature between summer and winter months in moderate climates.

High and unchanged sperm counts of Finnish men

Several recent reports have suggested that the sperm counts of normal men are declining in most countries. In this study the sperm counts of Finnish men, and their possible changes during the past 28 years, were investigated. The material consisted of semen samples from 238 normal healthy men of unknown fertility and 5481 men from infertile couples. The means (medians) of semen volume, sperm density and total sperm count in normal men were 3.3 (3.0) ml, 133.9 (94.0) x 10(6)/ml and 396.6 (309.0) x 10(6), respectively. These parameters and the relative frequency distribution of the sperm density were similar to those reported elsewhere in the 1940s. Multiple linear regression analysis revealed a significant decrease in semen volume, whereas sperm density and total sperm count of infertile men had not changed significantly during the past 28 years. In addition, no change in sperm counts was associated with the year of men's birth.

Have sperm counts been reduced 50 percent in 50 years? A statistical model revisited

OBJECTIVE

To reanalyze data that were used in a linear model to predict that mean sperm counts have been reduced globally by approximately 50% in the last 50 years.

DESIGN

The mean sperm counts and their temporal distribution were reanalyzed via several different statistical models (quadratic, spline fit, and stairstep).

CONCLUSION

There are several reasons why a published linear regression model is inappropriate to infer a 50% reduction in mean sperm counts in the last 50 years. These include [1] the potential selection biases that may have occurred with the 61 assembled studies such that they are not representative of their underlying populations; [2] the likely variability in collection methods, in particular, the lack of adherence to a minimum prescribed abstinence period, as has been stated for the largest study, which contained 29.7% of all the subjects included in the analysis; [3] the paucity of data in the first 30 years of the 50-year trend analysis; [4] the fact that if the last 20 years of data are examined, which contains 78.7% of all the studies and 88.1% of the total number of subjects, there is no decrease in sperm counts, in fact, sperm counts were observed to have increased; [5] the conflicting data from a large individual laboratory, which was not prone to the collection variability that likely occurred between the 61 studies, that did not suggest a decline in mean sperm count or seminal volume during a comparable time period, even though this laboratory published the data that were largely responsible for the high historical values in the linear model; and, most importantly, [6] the variety of other mathematical models that perform statistically better at describing the recent data than the linear model and thus offer substantially different hypotheses. The data are only robust during the last 20 years of the analysis, in which all the models, except the linear model, suggest constant or slightly increasing sperm counts.

Effects of cigarette smoking on human semen quality

The effects of cigarette smoking on sperm quality were evaluated from a group of males undergoing initial screening for infertility. Out of a total of 674 males, 618 (selected based on established criteria) were studied. Detailed smoking history was obtained by direct interview. Tests were conducted on semen characteristics (volume, sperm density, viability, motility, and morphology). Smokers had significantly poorer sperm density (p < .04), a lower percentage of normal sperm morphology (p < .001) and a higher percentage of headpiece spermatozoa defects (p < .01) compared with the nonsmokers. Significant trends were also observed for different categories of cigarette-years with sperm density, percentage of normal spermatozoa morphology, and percentage of spermatozoa with headpiece defect. Cigarette smoking appears to affect sperm density and the morphology of spermatozoa, especially the headpiece. A dose-response relationship of cigarette smoking and spermatogenesis is suggested.

Evidence for decreasing quality of semen during past 50 years

OBJECTIVE

To investigate whether semen quality has changed during the past 50 years.

DESIGN

Review of publications on semen quality in men without a history of infertility selected by means of Cumulated Index Medicus and Current List (1930-1965) and MEDLINE Silver Platter database (1966-August 1991).

SUBJECTS

14,947 men included in a total of 61 papers published between 1938 and 1991.

MAIN OUTCOME MEASURES

Mean sperm density and mean seminal volume.

RESULTS

Linear regression of data weighted by number of men in each study showed a significant decrease in mean sperm count from 113 x 10(6)/ml in 1940 to 66 x 10(6)/ml in 1990 (p < 0.0001) and in seminal volume from 3.40 ml to 2.75 ml (p = 0.027), indicating an even more pronounced decrease in sperm production than expressed by the decline in sperm density.

CONCLUSIONS

There has been a genuine decline in semen quality over the past 50 years. As male fertility is to some extent correlated with sperm count the results may reflect an overall reduction in male fertility. The biological significance of these changes is emphasised by a concomitant increase in the incidence of genitourinary abnormalities such as testicular cancer and possibly also cryptorchidism and hypospadias, suggesting a growing impact of factors with serious effects on male gonadal function.

Seasonal preovulatory overripeness ovopathy: a reappraisal of the concept

Seasonal Preovulatory Overripeness Ovopathy (SPOO) is one explanation for seasonal variations in the occurrence of congenital anomalies. This concept entails that during some seasons the preovulatory phase of the development of the human egg is lengthened, causing congenital anomalies. Although the concept of SPOO provides an innovative explanation for the etiology of congenital anomalies, its dissemination in the scientific world has been limited. The aim of this paper is to explain this limited dissemination through a critical examination of the concept itself. To do this we analyzed the degree in which this concept has a sufficient informative content and explanatory power, following criteria formulated by Popper. It is concluded that descriptions of the concept of SPOO are ambiguous. Thus the concept cannot be tested and has a limited informative content. The explanatory power of the SPOO concept remains unclear, in itself and relative to competing explanations. Further one of its basic assumptions, seasonal variation of the length of the preovulatory phase due to an endogenous mechanism, has been refuted. Future research should better be directed to causes of preovulatory overripeness ovapathy (OO) other than seasonality. This preovulatory OO offers an innovative view on the etiology of congenital anomalies.

Variation of semen quality in normal men

To examine the amount of variability in semen analysis results and whether there is any effect of season, 673 specimens provided by seven normal, healthy men (61-205 specimens/subject) over 72-324 weeks were assessed for sperm concentration, ejaculate volume, motility and motility index. Noticeable sample to sample variations were found. The largest proportion of the overall variance was due to within-subject differences, e.g., sperm concentration (54%), ejaculate volume (59%), percentage motility (96%) and motility index (74%). Although changes in semen-analysis results occurred over the year, no consistent trend was seen. No evidence was found to suggest that the differences were due to modifications of the methods employed by the laboratory, or to the change of season.

Cigarette smoking and sperm quality

The effect of cigarette smoking on conventional semen parameters (volume, total sperm count, sperm count/ml, total motility, progressive motility, morphology) was studied retrospectively in 90 healthy patients (50 non-smokers, 40 smokers) of our infertility clinic. Both groups, comparable in age, height and weight, were subdivided into two age groups (less than 28 years, greater than or equal to 28 years). Smokers were found to have sperm volumes significantly smaller than non-smokers of the same age. No additional effects on sperm parameters were found. Cigarette smoking revealed no detrimental effect on spermatogenesis.