Monthly variation in human semen quality in male partners of infertile women in the tropics

Monthly variations in semen parameters in a Sri Lankan population undergoing fertility evaluation

OBJECTIVE

Seasonal variations in semen quality are known to occur in temperate regions, but results regarding tropical areas remain inconclusive. The aim of this study was to determine whether monthly variations in semen parameters are present among men in a tropical region.

METHODS

Data were retrospectively collected from semen analyses of 3,000 men over a 10-year period, from 2012 to 2022. Analysis of variance and the independent-samples t-test were employed to observe variations in semen parameters throughout the entire period and between months, respectively.

RESULTS

The mean±standard deviation sperm concentration was significantly lower in June, at 42.5±31.4 million/mL, compared to other months. The highest sperm concentration was found in March, at 57.8±42.6 million/mL, constituting a mean difference of 15.3 million/mL between the lowest and highest concentrations. The total sperm count displayed a similar pattern of monthly variation, with a difference of 47.2 million between the highest and lowest months. No significant monthly differences were observed in other parameters, such as sperm motility, morphology, and semen volume.

CONCLUSION

Significant monthly variations in sperm concentration and total sperm count were evident in this Sri Lankan population. March, which displayed the highest sperm counts, is in the spring in temperate regions, while the month with the lowest counts, July, is part of the summer. Fluctuations in photoperiod appear to most strongly influence these variations.

Do seasonal variations in ambient temperature, humidity and daylight duration affect semen parameters? A retrospective analysis over eight years

We aimed to evaluate the possible effects of seasonal variation on semen parameters. We retrospectively analysed the data of 6,116 semen samples collected at a university hospital for eight years. The past ambient temperature, relative humidity and daylight duration records, and birth registry of the province were obtained to examine the relationship of seasonal changes in semen parameters with annual birth rates and environmental factors. The mean age was 33.03 ± 6.86 years. We found a significant difference between months for sperm concentration (p < .0001), total sperm count (p < .0001), progressively motile sperm count (p < .0001) and normal sperm morphology (p = .028). The sperm concentration and total count were significantly lower in July and August compared with December, May and June. The progressively motile sperm count in October was 23.6% less than the value of May. The temperature and temperature-humidity index were negatively correlated with semen parameters. The highest number of births was in the summer. However, no correlation was present between deliveries and the semen concentration regarding months (r_s  = 0.199, p = .083). In conclusion, we observed significant seasonal and monthly differences in sperm concentration, sperm count and progressively motile sperm count. Increased ambient temperature due to seasonal changes may be a detrimental factor for semen parameters.

Sperm physiology varies according to ultradian and infradian rhythms

The spermatozoon must be physiologically prepared to fertilize the egg, process called capacitation. Human sperm samples are heterogeneous in their ability to capacitate themselves, which leads to variability between samples from the same or different donors, and even along the seasons. Here we studied sperm variation in the capacitation state according to the ability of capacitated spermatozoa to acrosome react upon stimulation (% ARi) and to be recruited by chemotaxis (% Chex). Both indirect indicators of sperm capacitation increased along the incubation time with fluctuations. Those capacitated sperm recruited by chemotaxis showed an ultradian rhythm with a cycle every 2 h, which might be influenced by unknown intrinsic sperm factors. Two infradian rhythms of 12 months for the % ARi and of 6 months for % Chex were observed, which are associated with the joint action of temperature and photoperiod. Thus, to avoid false negative results, human sperm samples are recommended to be incubated for a long period (e.g. 18 h) preferably in spring time. This innovative point of view would lead to better comprehend human reproductive biology and to think experimental designs in the light of sperm cyclicity or to improve sperm aptitude for clinical purposes.

Environmental factors contributed to circannual rhythm of semen quality

We investigated whether human semen parameters present circannual rhythm or not, and whether environmental factors exert on semen quality. This retrospective study used data of patients mainly from Reproductive Medicine Center and Urology and Andrology Clinic of a general hospital in China. Sperm concentration and motility were measured by computer aided sperm analysis (CASA). Sperm morphology was scored based on the strict criteria (WHO, 2010). The Kruskal-Wallis rank test was used to investigate the relationship between semen parameters and season/month. Partial correlation coefficients were used to analyze the relationship between semen parameters and environmental factors. In this study, we found that sperm concentration and total amount per ejaculate were significantly lower in summer and higher in winter. But, sperm progressive motility and motility were significantly higher in spring and summer (from March to June), lower in autumn and winter (September and October). Unexpectedly, normal sperm morphology and mixed agglutination reaction (MAR) positive rate didn't vary along with season or month. Furthermore, temperature was negatively related to sperm concentration and total amount per ejaculate. Precipitation was positively associated with progressive motility and normal sperm morphology, but negatively related to sperm head defect percentage. The length of sunlight was positively related to progressive motility. The Air Quality Index (AQI) was positively associated with semen volume and sperm total amount per ejaculate. These suggest seasonal and monthly variation underlying some semen parameters.

Influence of indoor and outdoor temperatures on the fingertip blood flow rate

A total of 58 healthy subjects participated to elucidate the influence of indoor and outdoor temperatures on blood flow. After walking outdoors for 20 min, the blood flow rate of a subject was measured. The subject then entered a classroom and studied for 120 min, and afterwards, the blood flow rate was measured again. The subjects were exposed to outdoor temperature ranging from -2.5 to 33.7°C. During the summer, the average blood flow rate after walking outdoors was 45.95 ± 25.790 TPU (tissue perfusion units); after the class, this decreased to 36.14 ± 21.837 TPU (p<0.05). During the autumn, the blood flow rate decreased from 27.69 ± 12.334 TPU to 12.47 ± 12.255 TPU (p<0.001). When the outside air temperature was below 3°C, the blood flow rate indoors increased significantly from 6.74 ± 3.540 TPU to 13.95 ± 11.522 TPU (p<0.05). In a comfortable and healthy environment, the blood flow rate was not constant but fluctuated between 15 TPU and 40 TPU.

Association between urinary polycyclic aromatic hydrocarbon metabolites and sperm DNA damage: a population study in Chongqing, China

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs), a class of the most ubiquitous environmental contaminants, may reduce male reproductive functions, but the data from human population studies are very limited.

OBJECTIVES

We designed this study to determine whether environmental exposure to PAHs contributes to the alteration in semen quality, sperm DNA damage, and apoptosis in the general male human population.

METHODS

We measured urinary levels of four PAH metabolites and assessed semen quality, sperm apoptotic markers with Annexin V assay, and sperm DNA damage with comet assay in 232 men from Chongqing, China.

RESULTS

We found that increased urinary 2-hydroxynaphthalene (2-OHNa) levels were associated with increased comet parameters, including the percentage of DNA in the tail (tail%) [β coefficient = 13.26% per log unit 2-OHNa (micrograms per gram creatinine); 95% confidence interval (CI), 7.97-18.55]; tail length (12.25; 95% CI, 0.01-24.52), and tail distribution (7.55; 95% CI, 1.28-18.83). The urinary level of 1-hydroxypyrene was associated only with increased tail% (5.32; 95% CI, 0.47-10.17). Additionally, the increased levels of four urinary PAH metabolites were significantly associated with decreased vital Annexin V negative sperm counts. However, there was no significant association between urinary PAH metabolite levels and human semen parameters or morphology of the sperm samples.

CONCLUSIONS

Our data indicate that the environmental level of PAH exposure is associated with increased sperm DNA damage but not with semen quality. These findings suggest that exposure to PAHs may disrupt sperm DNA and thereby interfere with human male fertility.

Modelling of energy expended by free swimming spermatozoa in temperature-dependent viscous semen

Derived models of fertilization kinetics have relied upon estimates of the swimming velocity of spermatozoa from the insemination site to a fallopian tube. However, limited derivations are available describing the probability and energy expended when spermatozoa collide with one another. An analytic approach of spermatozoon motion in a linear viscoelastic fluid is adopted to simplify the derivation. The complex kinematics of motion of an inextensible flagellum is modelled as planar flagellar wave of small amplitude. In humans, a temperature difference is expected between the cooler tubal isthmus and the warmer tubal ampulla. Thus, fluidic characteristics of semen such as viscosity can vary along the female reproductive tract. The results suggest that the probability of spermatozoa colliding in relatively lower viscous semen increases by 64.87% for a 0.5 degrees C surge in temperature. Moreover, this increases for a denser concentration of spermatozoa due to the limited semen volume available to manoeuvre. In addition, the propulsive forces and shear stress were 39.35% lower in less viscous semen due to an increase in temperature of only 0.5 degrees C. Hence, the described derivations herein can assist in the understanding of work done by a normal motile spermatozoon in a pool of semen.

Semen quality of Asian men

After the controversial report by Carlsen et al. in 1992 showing a possible decline in human semen quality over the past 50 years, many laboratories investigated their own records of semen findings that had been kept for the past decades, and a significant decrease in sperm quality was reported from some laboratories, but not others. At the beginning of the 21st century, a definitive interpretation of this issue has not yet been offered; however, it seems plausible that there are large regional differences in semen quality. Decreases in semen quality have been reported from various regions around the world, and a concurrent rise in the incidence of other reproductive problems, such as testicular cancer and genital abnormalities, has been observed in many regions. However, most of the reports showing regional differences were from Western or Western-derived countries, despite the fact that Asia is the region with the highest population on earth. Recently we undertook a cross-sectional study on fertile men in Japan to describe the current status of semen quality of Japanese men. We took confounders into consideration to allow a comparison with a previous European study. Japanese fertile men proved to have a semen quality at the level of Danish men, who were reported to have the lowest level among the men examined in the European study. This low level of sperm concentration in fertile Japanese men may result from differences in lifestyle or other environmental factors, but we cannot rule out the possibility of ethnic differences caused by different genetic variation or combination. To address this issue we need more information on the reproductive function in Asian men, who have been reported to have certain differences in reproductive characteristics from Caucasian men. This article is an attempt to review our present knowledge concerning the current status of semen quality in healthy Asian men on the basis of the limited publications from Asia. (Reprod Med Biol 2007; 6: 185-193).

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 in a residential, geographic and age representative sample of healthy Chinese men

BACKGROUND

Population-based study of semen quality is rare in literature.

METHODS

Healthy men aged 20-60 years from six Chinese provinces were invited to participate in the study between December 2000 and November 2002. Posters were distributed in the participating counties to enroll 200 subjects from each province. Medians, percentiles, and proportions below lower threshold of the WHO criteria for semen parameters were calculated. Generalized linear models were used to examine the determinants of semen quality.

RESULTS

Semen samples from 1191 healthy Chinese men were collected and analysed. The medians (5th and 95th percentiles) were 2.3 ml (1.0-4.5) for semen volume, 65 x 10(6)/ml (20-150) for semen concentration, 154 x 10(6)/ejection (29-421) for sperm count, 19% (5-32) for rapid progressive motility, 46% (29-66) for progressive motility, 67% (47-81) for total motile spermatozoa, 70% (48-88) for sperm viability and 39% (23-76) for normal morphology. Many healthy Chinese men had semen parameter values below the lower threshold of the WHO criteria. Region, age, abstinence duration and season were important determinants of semen quality.

CONCLUSIONS

Chinese men have lower values of semen parameters according to WHO standard, and a lower threshold for normal semen parameters for Chinese men should be considered.

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.

Semen analysis in fertile patients undergoing vasectomy: reference values and variations according to age, length of sexual abstinence, seasonality, smoking habits and caffeine intake

CONTEXT AND OBJECTIVE

Recent studies have shown regional and population differences in semen characteristics. The objective was to establish reference values for semen analysis and to verify the effect that age, length of sexual abstinence, seasonality, smoking habits and coffee consumption have on fertile individuals' semen characteristics.

DESIGN AND SETTING

Prospective study in the Urology Division, Hospital das Clínicas, Universidade de São Paulo.

METHODS

Between September 1999 and August 2002, 500 fertile men requesting a vasectomy for sterilization purposes were asked to provide a semen sample before the vasectomy. We evaluated the effects of age, sexual abstinence, seasonality, smoking and coffee consumption on semen characteristics.

RESULTS

Compared with World Health Organization values, 87.2% of the patients presented sperm morphology below the normal level. A significant decline in semen volume, sperm motility and sperm morphology in patients over 45 years of age was observed. In patients with 5 days or more of abstinence, there was reduced sperm motility. The lowest values for sperm concentration, motility and morphology were observed in summer and the highest in winter. No differences in semen parameters relating to smoking were detected. Patients who drank six or more cups of coffee per day presented higher sperm motility.

CONCLUSIONS

Our sample had a very low percentage of normal sperm morphology. Only sperm morphology showed a high abnormality rate. Differences in semen parameters with regard to age, length of sexual abstinence, seasonality and coffee consumption were identified. No differences relating to smoking were detected.

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.

Impact of seasonal variation, age and smoking status on human semen parameters: The Massachusetts General Hospital experience

BACKGROUND: To investigate the relationship of human semen parameters with season, age and smoking status. METHODS: The present study used data from subjects recruited into an ongoing cross-sectional study on the relationship between environmental agents and semen characteristics. Our population consisted of 306 patients who presented to the Vincent Memorial Andrology Laboratory of Massachusetts General Hospital for semen evaluation. Sperm concentration and motility were measured with computer aided sperm analysis (CASA). Sperm morphology was scored using Tygerberg Kruger strict criteria. Regression analyses were used to investigate the relationships between semen parameters and season, age and smoking status, adjusting for abstinence interval. RESULTS: Sperm concentration in the spring was significantly higher than in winter, fall and summer (p < 0.05). There was suggestive evidence of higher sperm motility and percent of sperm with normal morphology in the spring than in the other seasons. There were no statistically significant relationships between semen parameters and smoking status, though current smokers tended to have lower sperm concentration. We also did not find a statistically significant relationship between age and semen parameters. CONCLUSIONS: We found seasonal variations in sperm concentration and suggestive evidence of seasonal variation in sperm motility and percent sperm with normal morphology. Although smoking status was not a significant predictor of semen parameters, this may have been due to the small number of current smokers in the study.

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.

Seasonal variation and age-related changes in human semen parameters

Although semen quality has been discussed extensively with regard to age and season in the andrology literature, the results vary and firm conclusions are still outstanding. To investigate seasonal and age-related variations in human semen parameters, we analyzed data that were collected from an andrology clinic population. We performed a retrospective review of 551 semen analysis records collected from 1989 to 2000 from the Vincent Memorial Andrology Laboratory at Massachusetts General Hospital. Semen volume, sperm concentration, total sperm count, motility, total motile sperm, and morphology significantly decreased as age increased. In addition, as age increased, the percentage of sperm with tail defects increased. Sperm concentration was significantly higher in winter (mean 157.9 million/mL) than in fall (mean 119.1 million/mL) (P <.05). The mean percentage of sperm with normal morphology was significantly higher in winter (9.2%) than in summer and spring (7.0% and 7.5%, respectively; P <.05). The mean percentage of sperm with head defects was significantly higher in fall and summer (74.0% and 72.3%, respectively) than in winter (68.6%; P <.05). Seasonal variations were found in sperm concentration and morphology, with higher sperm concentrations in winter than in fall, and a greater percentage of sperm with normal morphology in winter than in spring and summer. Sperm concentration was lowest in the fall, whereas the percentage of sperm with normal morphology was lowest in summer. Semen volume, sperm concentration, total sperm count, motility, total motile sperm, and morphology decreased as age increased.