The importance of employing stringent methods to recruit fertile male controls

Temporal trends in sperm count: a systematic review and meta-regression analysis of samples collected globally in the 20th and 21st centuries

BACKGROUND

Numerous studies have reported declines in semen quality and other markers of male reproductive health. Our previous meta-analysis reported a significant decrease in sperm concentration (SC) and total sperm count (TSC) among men from North America-Europe-Australia (NEA) based on studies published during 1981-2013. At that time, there were too few studies with data from South/Central America-Asia-Africa (SAA) to reliably estimate trends among men from these continents.

OBJECTIVE AND RATIONALE

The aim of this study was to examine trends in sperm count among men from all continents. The broader implications of a global decline in sperm count, the knowledge gaps left unfilled by our prior analysis and the controversies surrounding this issue warranted an up-to-date meta-analysis.

SEARCH METHODS

We searched PubMed/MEDLINE and EMBASE to identify studies of human SC and TSC published during 2014-2019. After review of 2936 abstracts and 868 full articles, 44 estimates of SC and TSC from 38 studies met the protocol criteria. Data were extracted on semen parameters (SC, TSC, semen volume), collection year and covariates. Combining these new data with data from our previous meta-analysis, the current meta-analysis includes results from 223 studies, yielding 288 estimates based on semen samples collected 1973-2018. Slopes of SC and TSC were estimated as functions of sample collection year using simple linear regression as well as weighted meta-regression. The latter models were adjusted for predetermined covariates and examined for modification by fertility status (unselected by fertility versus fertile), and by two groups of continents: NEA and SAA. These analyses were repeated for data collected post-2000. Multiple sensitivity analyses were conducted to examine assumptions, including linearity.

OUTCOMES

Overall, SC declined appreciably between 1973 and 2018 (slope in the simple linear model: -0.87 million/ml/year, 95% CI: -0.89 to -0.86; P < 0.001). In an adjusted meta-regression model, which included two interaction terms [time × fertility group (P = 0.012) and time × continents (P = 0.058)], declines were seen among unselected men from NEA (-1.27; -1.78 to -0.77; P < 0.001) and unselected men from SAA (-0.65; -1.29 to -0.01; P = 0.045) and fertile men from NEA (-0.50; -1.00 to -0.01; P = 0.046). Among unselected men from all continents, the mean SC declined by 51.6% between 1973 and 2018 (-1.17: -1.66 to -0.68; P < 0.001). The slope for SC among unselected men was steeper in a model restricted to post-2000 data (-1.73: -3.23 to -0.24; P = 0.024) and the percent decline per year doubled, increasing from 1.16% post-1972 to 2.64% post-2000. Results were similar for TSC, with a 62.3% overall decline among unselected men (-4.70 million/year; -6.56 to -2.83; P < 0.001) in the adjusted meta-regression model. All results changed only minimally in multiple sensitivity analyses.

WIDER IMPLICATIONS

This analysis is the first to report a decline in sperm count among unselected men from South/Central America-Asia-Africa, in contrast to our previous meta-analysis that was underpowered to examine those continents. Furthermore, data suggest that this world-wide decline is continuing in the 21st century at an accelerated pace. Research on the causes of this continuing decline and actions to prevent further disruption of male reproductive health are urgently needed.

Temporal trends in sperm count: a systematic review and meta-regression analysis

BACKGROUND

Reported declines in sperm counts remain controversial today and recent trends are unknown. A definitive meta-analysis is critical given the predictive value of sperm count for fertility, morbidity and mortality.

OBJECTIVE AND RATIONALE

To provide a systematic review and meta-regression analysis of recent trends in sperm counts as measured by sperm concentration (SC) and total sperm count (TSC), and their modification by fertility and geographic group.

SEARCH METHODS

PubMed/MEDLINE and EMBASE were searched for English language studies of human SC published in 1981-2013. Following a predefined protocol 7518 abstracts were screened and 2510 full articles reporting primary data on SC were reviewed. A total of 244 estimates of SC and TSC from 185 studies of 42 935 men who provided semen samples in 1973-2011 were extracted for meta-regression analysis, as well as information on years of sample collection and covariates [fertility group ('Unselected by fertility' versus 'Fertile'), geographic group ('Western', including North America, Europe Australia and New Zealand versus 'Other', including South America, Asia and Africa), age, ejaculation abstinence time, semen collection method, method of measuring SC and semen volume, exclusion criteria and indicators of completeness of covariate data]. The slopes of SC and TSC were estimated as functions of sample collection year using both simple linear regression and weighted meta-regression models and the latter were adjusted for pre-determined covariates and modification by fertility and geographic group. Assumptions were examined using multiple sensitivity analyses and nonlinear models.

OUTCOMES

SC declined significantly between 1973 and 2011 (slope in unadjusted simple regression models -0.70 million/ml/year; 95% CI: -0.72 to -0.69; P < 0.001; slope in adjusted meta-regression models = -0.64; -1.06 to -0.22; P = 0.003). The slopes in the meta-regression model were modified by fertility (P for interaction = 0.064) and geographic group (P for interaction = 0.027). There was a significant decline in SC between 1973 and 2011 among Unselected Western (-1.38; -2.02 to -0.74; P < 0.001) and among Fertile Western (-0.68; -1.31 to -0.05; P = 0.033), while no significant trends were seen among Unselected Other and Fertile Other. Among Unselected Western studies, the mean SC declined, on average, 1.4% per year with an overall decline of 52.4% between 1973 and 2011. Trends for TSC and SC were similar, with a steep decline among Unselected Western (-5.33 million/year, -7.56 to -3.11; P < 0.001), corresponding to an average decline in mean TSC of 1.6% per year and overall decline of 59.3%. Results changed minimally in multiple sensitivity analyses, and there was no statistical support for the use of a nonlinear model. In a model restricted to data post-1995, the slope both for SC and TSC among Unselected Western was similar to that for the entire period (-2.06 million/ml, -3.38 to -0.74; P = 0.004 and -8.12 million, -13.73 to -2.51, P = 0.006, respectively).

WIDER IMPLICATIONS

This comprehensive meta-regression analysis reports a significant decline in sperm counts (as measured by SC and TSC) between 1973 and 2011, driven by a 50-60% decline among men unselected by fertility from North America, Europe, Australia and New Zealand. Because of the significant public health implications of these results, research on the causes of this continuing decline is urgently needed.

Office falloposcopy; a tertiary level assessment for planning the management of infertile women

Thirty-nine women underwent Falloposcopic examination utilizing the linear eversion catheter. Indications for examination included bilateral and unilateral proximal and distal tubal occlusive disease, assessing the residual Fallopian tube after salpingectomy for ectopic pregnancy, and unexplained infertility. Seventy-three Fallopian tubes were available for examination, of which 72 (98.6%) were successfully cannulated. Sixty-eight ampullas were successfully visualized (94.4%). The mean duration of the examination was 24.7 minutes. Where proximal tubal disease was not suspected, 30.3% of oviducts were found to have a proximal lesion and 57.5% were found to have distal intratubal disease.

Risk factors for unexplained dyspermia in infertile men: a case-control study

This study was conducted to analyze risk factors for dyspermia in infertile subjects in a population of men attending outpatient services for infertility in Milan, Northern Italy. Between September 1989 and November 1990 we conducted a case-control study on risk factors for dyspermia. Cases included infertile men with a diagnosis of unexplained dyspermia consecutively observed for the first time during the study period at the Outpatient Service for Infertility of the First Obstetric and Gynecologic Clinic of the University of Milan. Specific work-up was done to exclude the major known or potential causes of dyspermia and infertility in patients and their partners. Two control groups were selected. The first included normospermic men of infertile couples with negative work-up for any disease that might affect fertility, observed in the same outpatient service where cases had been identified. The second control group included fertile men of unknown semen quality who were the partners of women who gave birth at term (> 37 w gestation) to health infants in randomly selected days at the same clinic. In comparison with those who have never smoked, current smokers were at increased risk of dyspermia versus both normospermic men of infertile couples and fertile men of unknown semen quality, and the risk increased with number of cigarettes smoked per day and duration of smoking. The risk of dyspermia increased with the number of cups of coffee drunk per day compared with men drinking no or one cup per day. Likewise, alcohol drinkers were at increased risk and the risk increased with number of drinks/d.(ABSTRACT TRUNCATED AT 250 WORDS)

Placental protein 14 levels in uterine flushing and plasma of women with unexplained infertility

OBJECTIVES

To measure concentrations of placental protein 14 (PP14) in uterine flushings and plasma samples obtained from patients with unexplained infertility and to compare the results of those of normal fertile women.

DESIGN

Prospective study.

SETTING

Infertility and gynaecology outpatient clinics at the Jessop Hospital for Women, Sheffield, United Kingdom.

PATIENTS

Sixteen patients with unexplained infertility and 12 normal fertile women who had been previously sterilized.

INTERVENTIONS

Daily monitoring of luteinizing hormone (LH) to detect the LH surge; uterine flushings and blood samples were obtained on days 7, 10, and 12 after the LH surge.

MAIN OUTCOME MEASURES

The measurement of PP14 concentration in uterine flushings and plasma samples throughout the luteal phase.

RESULTS

Levels of PP14 in uterine flushings of patients with unexplained infertility were significantly lower than those of normal fertile women on days LH +10 and LH +12. No significant differences were observed between the two groups in PP14 levels in uterine flushings on day LH +7 and plasma samples on days LH +7, LH +10, and LH +12.

CONCLUSIONS

Patients with unexplained infertility have reduced concentrations of PP14 in uterine flushings but not in plasma samples as compared with normal fertile women. Placental protein 14 measurement in uterine flushings may be a more valuable method of assessing endometrial function in infertile patients than plasma levels of the protein.

The contribution of a hidden male factor to unexplained infertility

OBJECTIVE

To assess sperm function in patients with unexplained infertility in comparison with normal fertile men.

DESIGN

Prospective study.

SETTING

Infertility outpatient clinic and donor insemination program, University Department of Obstetrics and Gynecology at the Jessop Hospital for Women, Sheffield, United Kingdom.

PATIENTS

Nineteen patients with unexplained infertility and nineteen normal fertile men from a donor insemination program.

MAIN OUTCOME MEASURES

Monitoring of reactive oxygen species generation; computerized assessment of the hyperactivated motility pattern of the spermatozoa under capacitating conditions, with and without the addition of follicular fluid (FF); evaluation of sperm-zona pellucida (ZP) binding.

RESULTS

Reactive oxygen species generation was not significantly different between the study and control group. Follicular fluid-induced hyperactivation (HA) was significantly lower in patients with unexplained infertility than in the donors, but no difference was found comparing spontaneous HA (without FF) between the two groups. Follicular fluid-induced HA was completely absent in 39% of infertile men and only one fertile man. A low sperm-ZP binding ratio (< or = 0.3) was observed in 28% (5/18) of patients with unexplained infertility. In all, nine infertile men (47%) had 0% FF-induced HA and/or low sperm-ZP binding ratio.

CONCLUSIONS

Assessing FF-induced HA and sperm-ZP binding may have clinical significance in distinguishing a subgroup of men with unexplained infertility with sperm function abnormalities in which the fertilizing capacity of the spermatozoa might be reduced. These patients cannot be identified by the conventional semen analysis. Both tests may also be useful in planning the appropriate treatment for couples with unexplained infertility.