Occupation and Semen Parameters in a Cohort of Fertile Men.

OBJECTIVE: We examined associations between occupation and semen parameters in demonstrably fertile men in the Study for Future Families. METHODS: Associations of occupation and workplace exposures with semen volume, sperm concentration, motility, and morphology were assessed using generalized linear modeling. RESULTS: Lower sperm concentration and motility were seen in installation, maintenance, and repair occupations. Higher exposure to lead, and to other toxicants, was seen in occupations with lower mean sperm concentrations (prevalence ratio for lead: 4.1; pesticides/insecticides: 1.6; solvents: 1.4). Working with lead for more than 3 months was associated with lower sperm concentration, as was lead exposure outside of work. CONCLUSIONS: We found evidence in demonstrably fertile men for reduced sperm quality with lead, pesticide/herbicide, and solvent exposure. These results may identify occupations where protective measures against male reproductive toxicity might be warranted.

Alcohol and male reproductive health: a cross-sectional study of 8344 healthy men from Europe and the USA.

STUDY QUESTION: Is there an association between alcohol intake and semen quality and serum reproductive hormones among healthy men from the USA and Europe? SUMMARY ANSWER: Moderate alcohol intake is not adversely associated with semen quality in healthy men, whereas it was associated with higher serum testosterone levels. WHAT IS KNOWN ALREADY: High alcohol intake has been associated with a wide range of diseases. However, few studies have examined the correlation between alcohol and reproductive function and most have been conducted in selected populations of infertile men or have a small sample size and the results have been contradictory. STUDY DESIGN, SIZE, DURATION: A coordinated international cross-sectional study among 8344 healthy men. A total of 1872 fertile men aged 18-45 years (with pregnant partners) from four European cities and four US states, and 6472 young men (most with unknown fertility) aged 18-28 years from the general population in six European countries were recruited. PARTICIPANTS/MATERIALS, SETTING, METHODS: The men were recruited using standardized protocols. A semen analysis was performed and men completed a questionnaire on health and lifestyle, including their intake of beer, wine and liquor during the week prior to their visit. Semen quality (semen volume, sperm concentration, percentage motile and morphologically normal sperm) and serum reproductive hormones (FSH, LH, testosterone, sex hormone-binding globulin, and inhibin B and free testosterone) were examined. MAIN RESULTS AND THE ROLE OF CHANCE: The participation rate for our populations was 20-30%. We found no consistent association between any semen variable and alcohol consumption, which was low/moderate in this group (median weekly intake 8 units), either for total consumption or consumption by type of alcohol. However, we found a linear association between total alcohol consumption and total or free testosterone in both groups of men. Young and fertile men who consumed >20 units of alcohol per week had, respectively, 24.6 pmol/l (95% confidence interval 16.3-32.9) and 19.7 pmol/l (7.1-32.2) higher free testosterone than men with a weekly intake between 1 and 10 units. Alcohol intake was not significantly associated with serum inhibin B, FSH or LH levels in either group of men. The study is the largest of its kind and has sufficient power to detect changes in semen quality and reproductive hormones. LIMITATIONS, REASONS FOR CAUTION: The participation rate was low, but higher than in most previous semen quality studies. In addition, the study was cross-sectional and the men were asked to recall their alcohol intake in the previous week, which was used as a marker of intake up to 3 months before. If consumption in that week differed from the typical weekly intake and the intake 3 months earlier, misclassification of exposure may have occurred. However, the men were unaware of their semen quality when they responded to the questions about alcohol intake. Furthermore, we cannot exclude that our findings are due to unmeasured confounders, including diet, exercise, stress, occupation and risk-taking behavior. WIDER IMPLICATIONS OF THE FINDINGS: Our study suggests that moderate alcohol intake is not adversely associated with semen quality in healthy men, whereas it was associated with higher serum testosterone levels which may be due to a changed metabolism of testosterone in the liver. Healthy men may therefore be advised that occasional moderate alcohol intake may not harm their reproductive health; we cannot address the risk of high alcohol consumption of longer duration or binge drinking on semen quality and male reproductive hormones. STUDY FUNDING/COMPETING INTERESTS: All funding sources were non-profitable and sponsors of this study played no role in the study design, in data collection, analysis, or interpretation, or in the writing of the article. The authors have no conflicts of interest.

Serum inhibin-b in fertile men is strongly correlated with low but not high sperm counts: a coordinated study of 1,797 European and US men.

OBJECTIVE: To describe associations between serum inhibin-b and sperm counts, adjusted for effect of time of blood sampling, in larger cohorts than have been previously reported. DESIGN: Cross-sectional studies of spermatogenesis markers. SETTING: Four European and four US centers. PATIENT(S): Fertile men (1,797) were included and examined from October 1996-February 2005. INTERVENTION(S): The study was observational and therefore without any intervention. MAIN OUTCOME MEASURE(S): Associations between inhibin-b and semen variables controlled for time of blood sampling and other covariates. RESULT(S): Inhibin-b decreased about 2.00% per hour from 8 am-12 pm and then about 3.25% per hour from 12 pm-4 pm. There was a strong positive association between inhibin-b levels less than 150 pg/mL and both sperm concentration and total sperm count (slopes of the regression lines were ß=0.011 and ß=0.013 for natural logarithm-transformed sperm concentration and total sperm count, respectively). For inhibin-b levels of 150-300 pg/mL the associations were not as steep (ß=0.002), but still significant. For inhibin-b levels more than 300 pg/mL there was little association to the sperm counts. Neither sperm motility nor morphology was significantly related to inhibin-b level in any group. CONCLUSION(S): Serum inhibin-b levels decrease nonlinearly during the daytime, and are positively correlated with sperm counts, but the predictive power is best when inhibin-b is low.

Practical semen analysis: from A to Z.

Accurate semen analysis is critical for decisions about patient care, as well as for studies addressing overall changes in semen quality, contraceptive efficacy and effects of toxicant exposure. The standardization of semen analysis is very difficult for many reasons, including the use of subjective techniques with no standards for comparison, poor technician training, problems with proficiency testing and a reluctance to change techniques. The World Health Organization (WHO) Semen handbook (2010) offers a vastly improved set of standardized procedures, all at a level of detail that will preclude most misinterpretations. However, there is a limit to what can be learned from words and pictures alone. A WHO-produced DVD that offers complete demonstrations of each technique along with quality assurance standards for motility, morphology and concentration assessments would enhance the effectiveness of the manual. However, neither the manual nor a DVD will help unless there is general acknowledgement of the critical need to standardize techniques and rigorously pursue quality control to ensure that laboratories actually perform techniques 'according to WHO' instead of merely reporting that they have done so. Unless improvements are made, patient results will continue to be compromised and comparison between studies and laboratories will have limited merit.

Semen quality in fertile men in relation to psychosocial stress.

OBJECTIVE: To examine the association between stressful life events and semen parameters. DESIGN: Cross-sectional analysis in a pregnancy cohort study. SETTING: Prenatal clinics in five U.S. cities. PATIENT(S): Fertile men (n = 744) in the Study for Future Families, a cohort study of pregnant women and their partners. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Sperm concentration, percent motile, and percent normal morphology and classification above/below World Health Organization (WHO) cutoffs for semen quality. RESULT(S): After adjusting for confounders, men reporting 2+ recent stressful life events had an increased risk of being classified below WHO thresholds for "normal" defined by concentration, motility, and morphology criteria compared with men reporting <2 stressful life events (odds ratio [OR] = 2.06; 95% confidence interval [CI], 1.18, 3.61; OR = 1.54; 95% CI, 1.04, 2.29; OR = 1.93; 95% CI, 1.02, 3.66 for concentration, motility and morphology, respectively). Men experiencing 2+ stressful life events had lower sperm concentration (log scale, beta = -0.25; 95% CI, -0.38, -0.11) and lower percent motile sperm (beta = -1.95; 95% CI, -3.98, 0.07), but percent normal morphology was less affected. CONCLUSION(S): These results suggest that stressful life events may be associated with decreased semen quality in fertile men. The experience of psychosocial stress may be a modifiable factor in the development of idiopathic infertility.

Standardized methods for semen evaluation in a multicenter research study.

Semen evaluation methodology is complex and difficult to standardize. Rigorously standardized laboratory protocols and strict quality control (QC) are essential for meaningful comparison of data from multiple sites. We describe the methods used for determination of semen volume, sperm concentration, and percent sperm motility in the Study for Future Families, a multicenter study of semen quality in the United States. Each of these 3 semen parameters was assessed using 2 techniques, which provided the opportunity to compare precision and assess suitability for multicenter studies. Detailed protocols were used, and technicians were centrally trained. A total of 509 semen evaluations were performed. Semen volume measured by weight was greater (P <.0001) than that determined by pipetting (3.7 +/- 1.6 mL vs 3.2 +/- 1.6 mL). Sperm concentration determined using hemacytometer chambers was consistently higher (P <.001) than that using disposable MicroCell chambers (81.0 x 10(6)/mL vs 65.9 x 10(6)/mL). Precision was slightly greater for the MicroCell chamber. The percentage of motile sperm was assessed by a simple counting technique as well as by the World Health Organization categorical method that assigns individual motile sperm to "a," "b," and "c" categories on the basis of progression. When these 3 categories were collapsed, the methods provided values that were not statistically different (P >.05), although the collapsed values tended to be higher (58.1% vs 51.6%) and less precise (CV 7.7% vs 4.1%) for the categorical method than for motility determined using the simple method. The data obtained in this study demonstrate the critical need for rigorous standardization of protocols and techniques for multicenter studies.

Quality control of laboratory methods for semen evaluation in a multicenter research study.

Rigorously standardized laboratory protocols and strict quality control (QC) are essential for meaningful comparisons between semen quality data from multiple sites. We describe our experience with the Study for Future Families (SFF), a multicenter study of semen quality in the United States. Detailed protocols were developed, and technicians from each study site attended a training session at the central laboratory. Technicians received blinded replicates from diluted semen specimens for counting by MicroCell and hemacytometer. Sperm motility was assessed using videotaped recordings for simple percent motility and categorical assessment of individual sperm progression as recommended by the World Health Organization (WHO). The mean intertechnician coefficient of variation for individual specimens was 12.6% for MicroCell counts, 15.2% for hemacytometer counts, and 10.5% for percent motility. Intratechnician coefficients of variation averaged 10.3% for MicroCell counts, 12.5% for hemacytometer counts, and 5.2% for percent motility. The average percent differences between the technicians' values and the central standard for individual specimens were 13.5%, 16.6%, and 11.9% for MicroCell counts, hemacytometer counts, and simple percent motility, respectively. We achieved our goal of maintaining mean intratechnician coefficients of variation and mean percent differences from the standard values of 15% or less for measurements of simple percent motility and sperm concentration by MicroCell. Standardization using the Improved Neubauer hemacytometer chamber proved more difficult. We were not successful in standardizing a method for categorical assessment of individual sperm progression.

Semen quality in relation to biomarkers of pesticide exposure.

We previously reported reduced sperm concentration and motility in fertile men in a U.S. agrarian area (Columbia, MO) relative to men from U.S. urban centers (Minneapolis, MN; Los Angeles, CA; New York, NY). In the present study we address the hypothesis that pesticides currently used in agriculture in the Midwest contributed to these differences in semen quality. We selected men in whom all semen parameters (concentration, percentage sperm with normal morphology, and percentage motile sperm) were low (cases) and men in whom all semen parameters were within normal limits (controls) within Missouri and Minnesota (sample sizes of 50 and 36, respectively) and measured metabolites of eight current-use pesticides in urine samples provided at the time of semen collection. All pesticide analyses were conducted blind with respect to center and case-control status. Pesticide metabolite levels were elevated in Missouri cases, compared with controls, for the herbicides alachlor and atrazine and for the insecticide diazinon [2-isopropoxy-4-methyl-pyrimidinol (IMPY)]; for Wilcoxon rank test, p = 0.0007, 0.012, and 0.0004 for alachlor, atrazine, and IMPY, respectively. Men from Missouri with high levels of alachlor or IMPY were significantly more likely to be cases than were men with low levels [odds ratios (ORs) = 30.0 and 16.7 for alachlor and IMPY, respectively], as were men with atrazine levels higher than the limit of detection (OR = 11.3). The herbicides 2,4-D (2,4-dichlorophenoxyacetic acid) and metolachlor were also associated with poor semen quality in some analyses, whereas acetochlor levels were lower in cases than in controls (p = 0.04). No significant associations were seen for any pesticides within Minnesota, where levels of agricultural pesticides were low, or for the insect repellent DEET (N,N-diethyl-m-toluamide) or the malathion metabolite malathion dicarboxylic acid. These associations between current-use pesticides and reduced semen quality suggest that agricultural chemicals may have contributed to the reduction in semen quality in fertile men from mid-Missouri we reported previously.

Geographic differences in semen quality of fertile U.S. males.

Although geographic variation in semen quality has been reported, this is the first study in the United States to compare semen quality among study centers using standardized methods and strict quality control. We evaluated semen specimens from partners of 512 pregnant women recruited through prenatal clinics in four U.S. cities during 1999-2001; 91% of men provided two specimens. Sperm concentration, semen volume, and motility were determined at the centers, and morphology was assessed at a central laboratory. Study protocols were identical across centers, and quality control was rigorously maintained. Sperm concentration was significantly lower in Columbia, Missouri, than in New York, New York; Minneapolis, Minnesota; and Los Angeles, California. Mean counts were 58.7, 102.9, 98.6, and 80.8 X 10(6)/mL (medians 53.5, 88.5, 81.8, and 64.8 X 10(6)/mL) in Missouri, New York, Minnesota, and California, respectively. The total number of motile sperm was also lower in Missouri than in other centers: 113, 196, 201, and 162 X 10(6) in Missouri, New York, Minnesota, and California, respectively. Semen volume and the percent morphologically normal sperm did not differ appreciably among centers. These between-center differences remained significant in multivariate models that controlled for abstinence time, semen analysis time, age, race, smoking, history of sexually transmitted disease, and recent fever (all p-values < 0.01). Confounding factors and differences in study methods are unlikely to account for the lower semen quality seen in this mid-Missouri population. These data suggest that sperm concentration and motility may be reduced in semirural and agricultural areas relative to more urban and less agriculturally exposed areas.

Epidemiologic studies of human semen quality: considerations for study design.

Few empirical data exist on the characteristics of subjects who provide semen specimens in epidemiologic studies. The objective of this investigation was to determine participation rates and potential biases in a contemporary study of human semen quality. Subjects (n = 268) are a subset of the Child Health and Development Studies. Their mothers enrolled between 1960 and 1963 during pregnancy. Archived prenatal serum samples, prenatal and birth records, placental examinations, and follow-up for growth and development through adulthood are available. Sons were aged 36-39 years at the time of this study. Respondents to the initial mailing and nonrespondents, who were subsequently traced and recruited, differed in semen parameters, including sperm concentration (78.3 x 10(6)/ml for respondents vs. 37.2; p = 0.003) and the percentage of normal morphology according to the 1987 criteria of the World Health Organization (58.7% for respondents vs. 53.3%; p = 0.04). The authors conclude that researchers designing population-based studies of semen parameters should expect nonrepresentative samples. Adaptation of the design to anticipate and mitigate bias and to maximize efficiency can yield scientifically sound information. Recommendations for study designs are discussed.