Time to pregnancy and life expectancy: a cohort study of 18 796 pregnant couples

STUDY QUESTION

Is fecundity, measured as time to pregnancy (TTP), associated with mortality in parents?

SUMMARY ANSWER

Prolonged TTP is associated with increased mortality in both mothers and fathers in a dose-response manner.

WHAT IS KNOWN ALREADY

Several studies have linked both male and female fecundity to mortality. In women, infertility has been linked to several diseases, but studies suggest that the underlying conditions, rather than infertility, increase mortality.

STUDY DESIGN, SIZE, DURATION

A prospective cohort study was carried out on 18 796 pregnant couples, in which the pregnant women attended prophylactic antenatal care between 1973 and 1987 at a primary and tertiary care unit. The couples were followed in Danish mortality registers from their child's birth date until death or until 2018. The follow-up period was up to 47 years, and there was complete follow-up until death, emigration or end of study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

At the first antenatal visit, the pregnant women were asked to report the time to the current pregnancy. Inclusion was restricted to the first pregnancy, and TTP was categorised into <12 months, ≥12 months, not planned, and not available. In sub-analyses, TTP ≥12 was further categorized into 12-35, 36-60, and >60 months. Information for parents was linked to several Danish nationwide health registries. Survival analysis was used to estimate the hazard ratios (HRs) with a 95% CI for survival and adjusted for age at the first attempt to become pregnant, year of birth, socioeconomic status, mother's smoking during pregnancy, and mother's BMI.

MAIN RESULTS AND THE ROLE OF CHANCE

Mothers and fathers with TTP >60 months survived, respectively, 3.5 (95% CI: 2.6-4.3) and 2.7 (95% CI: 1.8-3.7) years shorter than parents with a TTP <12 months. The mortality was higher for fathers (HR: 1.21, 95% CI: 1.09-1.34) and mothers (HR: 1.29, 95% CI: 1.12-1.49) with TTP ≥12 months compared to parents with TTP <12 months. The risk of all-cause mortality during the study period increased in a dose-response manner with the highest adjusted HR of 1.98 (95% CI: 1.62-2.41) for fathers and 2.03 (95% CI: 1.56-2.63) for mothers with TTP >60 months. Prolonged TTP was associated with several different causes of death in both fathers and mothers, indicating that the underlying causes of the relation between fecundity and survival may be multi-factorial.

LIMITATIONS, REASONS FOR CAUTION

A limitation is that fecundity is measured using a pregnancy-based approach. Thus, the cohort is conditioned on fertility success and excludes sterile couples, unsuccessful attempts and spontaneous abortions. The question used to measure TTP when the pregnant woman was interviewed at her first attended prophylactic antenatal care: 'From the time you wanted a pregnancy until it occurred, how much time passed?' could potentially have led to serious misclassification if the woman did not answer on time starting unprotected intercourse but on the start of wishing to have a child.

WIDER IMPLICATIONS OF THE FINDINGS

We found that TTP is a strong marker of survival, contributing to the still-emerging evidence that fecundity in men and women reflects their health and survival potential.

STUDY FUNDING/COMPETING INTEREST(S)

The authors acknowledge an unrestricted grant from Ferring. The funder was not involved in the study design, collection, analysis, interpretation of data, the writing of this article, or the decision to submit it for publication. M.L.E. is an advisor to Ro, VSeat, Doveras, and Next.

TRIAL REGISTRATION NUMBER

N/A.

The association between in-utero exposure to stressful life events during pregnancy and male reproductive function in a cohort of 20-year-old offspring: The Raine Study

STUDY QUESTION

Is exposure to gestational stress in the critical time window for the normal differentiation and growth of male reproductive tissue associated with male reproductive function in offspring in later life?

SUMMARY ANSWER

Exposure to stressful life events (SLEs) in early, but not late gestation, are associated with reduced adult male reproductive function, consistent with the hypothesis that events during early prenatal life programme adult male reproductive function.

WHAT IS ALREADY KNOWN

Animal studies suggest that gestational stress may impact on the reproductive function of male offspring, but human evidence is sparse.

STUDY DESIGN, SIZE, DURATION

Using a prospective longitudinal cohort, we examined the association between number and type of maternal stressors during pregnancy in both early and late gestation and reproductive function in 643 male Generation 2 (offspring) at age 20 years. Mothers and their male Generation 2 (offspring) from The Raine Study participated. Mothers prospectively reported SLEs during pregnancy recorded at gestational weeks 18 and 34 using a standardized 10-point questionnaire.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The 643 male Generation 2 (offspring) underwent testicular ultrasound examination and semen analysis and provided serum for reproductive hormone analysis. Multivariate linear regression analysis was used to examine associations.

MAIN RESULTS AND ROLE OF CHANCE

Of 643 recruited males, 407 (63%) were exposed to at least one SLE in early gestation. Fewer SLEs were reported in late gestation (n = 343, 53%). Maternal SLE exposure in early gestation was negatively associated with total sperm count (β = -0.31, 95% CI -0.58; -0.03), number of progressive motile sperm (β = -0.15, 95% CI -0.31; 0.00) and morning serum testosterone concentration (β = -0.04, 95% CI -0.09; -0.00). No similar effects of maternal SLE exposure in late pregnancy were detected. The large sample size and an objective detailed direct assessment of adult male reproductive function with strict external quality control for sperm quality, as well as detailed prospectively collected information on prenatal SLEs in two distinct time windows of pregnancy reported by the women in early and late gestation along with other risk factors, imply minimal possibility of recall, information bias and selection bias. When assessing our results, we adjusted for a priori chosen confounders, but residual confounding or confounding by factors unbeknown to us cannot be ruled out.

LIMITATIONS, REASONS FOR CAUTION

It is not possible to measure how SLEs impacted differently on the mother's experience or perception of stress. Resilience (coping) gradients may alter cortisol levels and thus modify the associations we observed and the mothers' own perception of stress severity may have provided a more precise estimate of her exposure.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings suggest that exposure to SLEs in early, but not late gestation, are associated with reduced adult male reproductive function. Improved support for women with exposure to SLEs during pregnancy, particularly during the first trimester, may improve the reproductive health of their male offspring in later life. Intervention studies of improved pregnancy support could provide more insight into this association and more information is needed about the potential specific epigenetic mechanisms underlying this association.

STUDY FUNDING/COMPETING INTEREST(S)

The male fertility sub-study was funded by NHMRC Grant 634 457. The core management of the Raine Study is funded by University of Western Australia, Curtin University, Telethon Kids Institute, Women and Infants Research Foundation, Edith Cowan University, Murdoch University, The University of Notre Dame Australia and Raine Medical Research foundation. Dr Bräuner's salary was supported by Læge Sofus Carl Emil Friis og Hustru Olga Doris Friis foundation in Denmark. All authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Bisphenol A Diglycidyl Ether (BADGE) and Bisphenol Analogs, but Not Bisphenol A (BPA), Activate the CatSper Ca2+ Channel in Human Sperm

Aim: Evidence suggests that bisphenol A diglycidyl ether (BADGE), bisphenol A (BPA), and BPA analogs can interfere with human male fertility. However, the effect directly on human sperm function is not known. The CatSper Ca²⁺ channel in human sperm controls important sperm functions and is necessary for normal male fertility. Environmental chemicals have been shown to activate CatSper and thereby affect Ca²⁺ signaling in human sperm. BPA has previously been investigated for effects on Ca²⁺ signaling human sperm, whereas the effects of other BPA analogs are currently unknown. The aim of this study is thus to characterize the effect of BADGE, BPA, and the eight analogs BPG, BPAF, BPC, BPB, BPBP, BPE, BPF, BPS on Ca²⁺ signaling, and CatSper in human sperm. Methods: Direct effects of the bisphenols on Ca²⁺ signaling in human sperm cells were evaluated using a Ca²⁺ fluorimetric assay measuring changes in intracellular Ca²⁺. Effects via CatSper were assessed using the specific CatSper inhibitor RU1968. Effects on human sperm function was assessed using an image cytometry-based acrosome reaction assay and the modified Kremer's sperm-mucus penetration assay. Results: At 10 μM the bisphenols BPG, BPAF, BPC, BADGE, BPB, and BPBP induced Ca²⁺ signals in human sperm cells, whereas BPE, BPF, BPS, and BPA had no effect. The efficacy of the chemicals at 10 μM is BPG > BPAF > BPC > BADGE > BPB > BPBP. Dose-response relations of BPG, BPAF, BPC, BADGE, BPB, and BPBP yielded EC50-values in the nM-μM range. The induced Ca²⁺ signals were almost completely abolished using the CatSper inhibitor RU1968, indicating an effect of the bisphenols on CatSper. All bisphenols, except BPBP, were found to dose-dependently inhibit progesterone-induced Ca²⁺ signals, with BPG and BPAF displaying inhibition even in low μM doses. BPG and BPAF were shown to affect human sperm function in a progesterone-like manner. Conclusion: Our results show that the bisphenols BPG, BPAF, BPC, BADGE, BPB, and BPBP can affect Ca²⁺ signaling in human sperm cells through activation of CatSper. This could potentially disrupt human sperm function by interfering with normal CatSper-signaling and thus be a contributing factor in human infertility, either alone or in mixtures with other chemicals.

Semen quality of young men in Switzerland: a nationwide cross-sectional population-based study

BACKGROUND

Sperm counts have been steadily decreasing over the past five decades with regional differences in the Western world. The reasons behind these trends are complex, but numerous insights indicate that environmental and lifestyle factors are important players.

OBJECTIVE

To evaluate semen quality and male reproductive health in Switzerland.

MATERIALS AND METHODS

A nationwide cross-sectional study was conducted on 2523 young men coming from all regions of Switzerland, recruited during military conscription. Semen volume, sperm concentration, motility, and morphology were analyzed. Anatomy of the genital area and testicular volume was recorded. Testicular cancer incidence rates in the general population were retrieved from Swiss regional registries.

RESULTS

Median sperm concentration adjusted for period of sexual abstinence was 48 million/mL. Comparing with the 5th percentile of the WHO reference values for fertile men, 17% of men had sperm concentration below 15 million/mL, 25% had less than 40% motile spermatozoa, and 43% had less than 4% normal forms. Disparities in semen quality among geographic regions, urbanization rates, and linguistic areas were limited. A larger proportion of men with poor semen quality had been exposed in utero to maternal smoking. Furthermore, testicular cancer incidence rates in the Swiss general population increased significantly between 1980 and 2014.

DISCUSSION

For the first time, a systematic sampling among young men has confirmed that semen quality is affected on a national level. The median sperm concentration measured is among the lowest observed in Europe. No specific geographical differences could be identified. Further studies are needed to determine to what extent the fertility of Swiss men is compromised and to evaluate the impact of environmental and lifestyle factors.

CONCLUSION

A significant proportion of Swiss young men display suboptimal semen quality with only 38% having sperm concentration, motility, and morphology values that met WHO semen reference criteria.

Synergistic activation of CatSper Ca2+ channels in human sperm by oviductal ligands and endocrine disrupting chemicals

STUDY QUESTION

Does the chemosensory activation of CatSper Ca2+ channels in human sperm give rise to additive, sub-additive or even synergistic actions among agonists?

SUMMARY ANSWER

We show that oviductal ligands and endocrine disrupting chemicals (EDCs) activate human CatSper highly synergistically.

WHAT IS KNOWN ALREADY

In human sperm, the sperm-specific CatSper channel controls the intracellular Ca2+ concentration and, thereby, several crucial stages toward fertilization. CatSper is activated by oviductal ligands and structurally diverse EDCs. The chemicals mimic the action of the physiological ligands, which might interfere with the precisely coordinated sequence of events underlying fertilization.

STUDY DESIGN, SIZE, DURATION

For both oviductal ligands and EDCs, we examined in quantitative terms whether stimulation of human sperm in vitro with mixtures results in additive, sub-additive or synergistic actions.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We studied activation of CatSper in sperm of healthy volunteers, using kinetic Ca2+ fluorimetry and patch-clamp recordings. The combined action of progesterone and prostaglandins and of the EDCs benzylidene camphor sulfonic acid (BCSA) and α-Zearalenol was evaluated by curve-shift analysis, curvilinear isobolographic analysis and the combination-index method.

MAIN RESULTS AND THE ROLE OF CHANCE

Analysis of the action of progesterone/prostaglandin and BCSA/α-Zearalenol mixtures in human sperm by fluorimetry revealed that the oviductal ligands and EDCs both evoke Ca2+ influx via CatSper in a highly synergistic fashion. Patch-clamp recordings of CatSper currents in human sperm corroborated the synergistic ligand-activation of the channel.

LIMITATIONS, REASONS FOR CAUTION

This is an in vitro study. Future studies have to assess the physiological relevance in vivo.

WIDER IMPLICATIONS OF THE FINDINGS

These findings indicate that the fertilization process is orchestrated by multiple oviductal CatSper agonists that act in concert to control the behavior of sperm. Moreover, our results substantiate the concerns regarding the negative impact of EDCs on male reproductive health. So far, safety thresholds like the "No Observed Adverse Effect Level (NOAEL)" or "No Observed Effect Concentration (NOEC)" are set for individual EDCs. Our finding that EDCs act synergistically in human sperm challenges the validity of this procedure.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the German Research Foundation (SFB 645; CRU326), the Cells-in-Motion (CiM) Cluster of Excellence, Münster, (FF-2016-17), the 'Innovative Medical Research' of the University of Münster Medical School (BR121507), an EDMaRC research grant from the Kirsten and Freddy Johansen's Foundation, and the Innovation Fund Denmark (InnovationsFonden; 14-2013-4). The authors have no competing financial interests.

EDC IMPACT: Chemical UV filters can affect human sperm function in a progesterone-like manner

Human sperm cell function must be precisely regulated to achieve natural fertilization. Progesterone released by the cumulus cells surrounding the egg induces a Ca²⁺ influx into human sperm cells via the CatSper Ca²⁺-channel and thereby controls sperm function. Multiple chemical UV filters have been shown to induce a Ca²⁺ influx through CatSper, thus mimicking the effect of progesterone on Ca²⁺ signaling. We hypothesized that these UV filters could also mimic the effect of progesterone on sperm function. We examined 29 UV filters allowed in sunscreens in the US and/or EU for their ability to affect acrosome reaction, penetration, hyperactivation and viability in human sperm cells. We found that, similar to progesterone, the UV filters 4-MBC, 3-BC, Meradimate, Octisalate, BCSA, HMS and OD-PABA induced acrosome reaction and 3-BC increased sperm penetration into a viscous medium. The capacity of the UV filters to induce acrosome reaction and increase sperm penetration was positively associated with the ability of the UV filters to induce a Ca²⁺ influx. None of the UV filters induced significant changes in the proportion of hyperactivated cells. In conclusion, chemical UV filters that mimic the effect of progesterone on Ca²⁺ signaling in human sperm cells can similarly mimic the effect of progesterone on acrosome reaction and sperm penetration. Human exposure to these chemical UV filters may impair fertility by interfering with sperm function, e.g. through induction of premature acrosome reaction. Further studies are needed to confirm the results in vivo.

Chemical UV Filters Mimic the Effect of Progesterone on Ca2+ Signaling in Human Sperm Cells

Progesterone released by cumulus cells surrounding the egg induces a Ca²⁺ influx into human sperm cells via the cationic channel of sperm (CatSper) Ca²⁺ channel and controls multiple Ca²⁺-dependent responses essential for fertilization. We hypothesized that chemical UV filters may mimic the physiological action of progesterone on CatSper, thus affecting Ca²⁺ signaling in human sperm cells. We examined 29 UV filters allowed in sunscreens in the United States and/or the European Union for their ability to induce Ca²⁺ signals in human sperm by applying measurements of the intracellular free Ca²⁺ concentration. We found that 13 UV filters induced a significant Ca²⁺ signal at 10 μM. Nine UV filters induced Ca²⁺ signals primarily by activating the CatSper channel. The UV filters 3-benzylidene camphor (3-BC) and benzylidene camphor sulfonic acid competitively inhibited progesterone-induced Ca²⁺ signals. Dose-response relations for the UV filters showed that the Ca²⁺ signal-inducing effects began in the nanomolar-micromolar range. Single-cell Ca²⁺ measurements showed a Ca²⁺ signal-inducing effect of the most potent UV filter, 3-BC, at 10 nM. Finally, we demonstrated that the 13 UV filters acted additively in low-dose mixtures to induce Ca²⁺ signals. In conclusion, 13 of 29 examined UV filters (44%) induced Ca²⁺ signals in human sperm. Nine UV filters primarily activated CatSper and thereby mimicked the effect of progesterone. The UV filters 3-BC and benzylidene camphor sulfonic acid competitively inhibited progesterone-induced Ca²⁺ signals. In vivo exposure studies are needed to investigate whether UV filter exposure affects human fertility.

Evidence that active demethylation mechanisms maintain the genome of carcinoma in situ cells hypomethylated in the adult testis

BACKGROUND

Developmental arrest of fetal germ cells may lead to neoplastic transformation and formation of germ cell tumours via carcinoma in situ (CIS) cells. Normal fetal germ cell development requires complete erasure and re-establishment of DNA methylation. In contrast to normal spermatogonia, the genome of CIS cells remains unmethylated in the adult testis. We here investigated the possible active and passive pathways that can sustain the CIS genome hypomethylated in the adult testis.

METHODS

The levels of 5-methyl-cytosine (5mC) and 5-hydroxy-methyl-cytosine (5hmC) in DNA from micro-dissected CIS cells were assessed by quantitative measurements. The expression of TET1, TET2, APOBEC1, MBD4, APEX1, PARP1, DNMT1, DNMT3A, DNMT3B and DNMT3L in adult testis specimens with CIS and in human fetal testis was investigated by immunohistochemistry and immunofluorescence.

RESULTS

DNA from micro-dissected CIS cells contained very low levels of 5hmC produced by ten eleven translocation (TET) enzymes. CIS cells and fetal germ cells expressed the suggested initiator of active demethylation, APOBEC1, and the base excision repair proteins MBD4, APEX1 and PARP1, whereas TETs - the alternative initiators were absent. Both maintenance and de novo methyltransferases were detected in CIS cells.

CONCLUSION

The data are consistent with the presence of an active DNA de-methylation pathway in CIS cells. The hypomethylated genome of CIS cells may contribute to phenotypic plasticity and invasive capabilities of this testicular cancer precursor.

Changes in anti-Müllerian hormone (AMH) throughout the life span: a population-based study of 1027 healthy males from birth (cord blood) to the age of 69 years

CONTEXT

Anti-Müllerian hormone (AMH), which is secreted by immature Sertoli cells, triggers the involution of the fetal Müllerian ducts. AMH is a testis-specific marker used for diagnosis in infants with ambiguous genitalia or bilateral cryptorchidism.

AIM

The aim of the study was to describe the ontogeny of AMH secretion through life in healthy males.

SETTING

This was a population-based study of healthy volunteers.

PARTICIPANTS

PARTICIPANTS included 1027 healthy males from birth (cord blood) to 69 yr. A subgroup was followed up longitudinally through the infantile minipuberty [(in cord blood, and at 3 and 12 months), n=55] and another group through puberty [(biannual measurements), n=83].

MAIN OUTCOME MEASURES

Serum AMH was determined by a sensitive immunoassay. Serum testosterone, LH, and FSH were measured, and pubertal staging was performed in boys aged 6 to 20 yr (n=616).

RESULTS

Serum AMH was above the detection limit in all samples with a marked variation according to age and pubertal status. The median AMH level in cord blood was 148 pmol/liter and increased significantly to the highest observed levels at 3 months (P<0.0001). AMH declined at 12 months (P<0.0001) and remained at a relatively stable level throughout childhood until puberty, when AMH declined progressively with adults exhibiting 3-4% of infant levels.

CONCLUSION

Based on this extensive data set, we found detectable AMH serum levels at all ages, with the highest measured levels during infancy. At the time of puberty, AMH concentrations declined and remained relatively stable throughout adulthood. The potential physiological role of AMH and clinical applicability of AMH measurements remain to be determined.