P–741 Fetal exposure to maternal perceived stress and male reproductive function in a cohort of young adults

Study question

Is exposure to maternal perceived stress during pregnancy associated with reproductive function in adult male offspring?

Summary answer

While maternal perceived stress was prevalent in the first trimesters of pregnancy, our preliminary findings indicate little association with reproductive function in young men.

What is known already

Though studies in animals point to a connection between prenatal exposure to maternal stress and reproductive function in offspring, the underlying biological mechanisms generating a deficit remain largely unclear. In humans, the few available studies focus on exposure to bereavement or other relatively strong objective stressful life events. Our individual perception of stress is, however, more likely the sum of a complex process involving both the actual input, previous experiences, coping strategies and support from our surroundings.

Study design, size, duration

Young men and their mothers were identified through records from the Danish National Birth Cohort (DNBC). Information on exposure, i.e. maternal perceived life and emotional stress, was available from telephone interviews conducted at approximately 30 weeks of gestation (1996 to 2001). Recruitment of the young men lasted from 2017 to 2019 with 1058 participants enrolled in the final FEPOS cohort.

Participants/materials, setting, methods

Each of the 1058 men in the FEPOS cohort completed an online questionnaire and clinical examinations and provided a blood and semen sample. Information on potential pre- and postnatal confounders was retrieved from the DNBC, the Danish National Patient Register and the Danish Medical Birth Register. We applied negative binomial regression models to examine associations between maternal perceived life and emotional stress scores and semen quality, testicular size and reproductive hormones among the young men.

Main results and the role of chance

Among the 1052 young men included in preliminary analyses, the majority was exposed to maternal perceived life and/or emotional stress (76% and 83%, respectively) during the first trimesters. Life stress was predominantly related to the actual pregnancy (48%), maternal disease (19%) or occupational conditions (33%). Emotional stress included especially being touchy (58%), sad (38%) or tense (36%), covering aspects of both stress, depression and anxiety. Overall, results indicate little association between maternal stress scores and measures of semen quality and testicular size. Our study involves a large cohort with prospectively collected exposure data and direct measures of several male reproductive outcomes. We applied inverse probability weighting to account for selection into the FEPOS cohort and included a range of a priori selected maternal confounders in our models.

Limitations, reasons for caution

The male fetus may be particularly sensitive to exposure during the differentiation of reproductive tissues (8–14 weeks of gestation). Our self-reported measures of exposure cover the first 30 weeks of gestation. Absence of association may, thus, be due to a lack of specific information on timing of symptoms.

Wider implications of the findings: While our preliminary findings may appear reassuring, further efforts to improve our understanding of maternal stress in relation to fetal health and potential consequences later in life are needed.

Trial registration number

Not applicable

Birth weight for gestational age and the risk of infertility: a Danish cohort study

STUDY QUESTION

Is birth weight for gestational age associated with infertility in adulthood among men and women?

SUMMARY ANSWER

Being born small for gestational age (SGA) was associated with infertility in adulthood among men.

WHAT IS KNOWN ALREADY

Fetal growth restriction may affect fertility, but results from previous studies have been inconsistent.

STUDY DESIGN, SIZE, DURATION

In this population-based cohort study, we used data from a Danish birth cohort, including 5594 men and 5342 women born between 1984 and 1987. Information on infertility was obtained from Danish health registers during the period from the participants' 18th birthday and up until 31 December 2017.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants were men and women born in two Danish municipalities, Aalborg and Odense. Information on birth weight and gestational age was obtained from birth records, and information on infertility diagnoses and fertility treatment was retrieved from the Danish National Patient Registry (NPR) and the Danish In Vitro Fertilisation (IVF) registry. Information on potential maternal confounders was obtained from questionnaires during pregnancy and was included in adjusted analyses. Logistic regression analysis was used to estimate crude and adjusted odds ratios (ORs) with 95% confidence intervals (CIs) for infertility according to birth weight for gestational age.

MAIN RESULTS AND THE ROLE OF CHANCE

Men born SGA had a 55% higher risk of being diagnosed with or treated for infertility compared to men born appropriate for gestational age (AGA) (adjusted OR = 1.55, 95% CI: 1.09-2.21). The association attenuated after exclusion of men born with hypospadias or cryptorchidism (OR = 1.37, 95% CI: 0.93-2.01). No association was found between women's birth weight for gestational age and risk of infertility (adjusted OR = 1.00, 95% CI: 0.73-1.37).

LIMITATIONS, REASONS FOR CAUTION

Estimation of gestational age is associated with some uncertainty and might have caused non-differential misclassification. The study design implicitly assumed similar distribution of reproductive and health-seeking behaviour across the groups that were compared.

WIDER IMPLICATIONS OF THE FINDINGS

Men born SGA had a higher risk of infertility. Genital malformations may account for part of the observed association, but this must be explored further.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by Health, Aarhus University. No competing interests are declared.

TRIAL REGISTRATION NUMBER

N/A.

Serum concentrations of organochlorine compounds and predictors of exposure in children living in agricultural communities from South-Eastern Spain

BACKGROUND

Information on exposure levels to organochlorine compounds (OCs) in child population is limited, despite their greater vulnerability to the adverse health effects of these chemicals.

OBJECTIVE

To determine serum concentrations of 10 OCs (including organochlorine pesticides and polychlorinated biphenyls -PCBs-) in children living in agricultural communities from Almería (South-Eastern Spain), and to identify the main predictors of exposure related to socio-economic characteristics, diet and lifestyle.

METHODS

A cross-sectional study was conducted on 133 children aged 6-11 years selected from public schools of the study area. OCs compounds were determined in serum samples by GC/ECD. Anthropometric measures were obtained during sample collection. Information on sociodemographic characteristics, parental occupation, residential history, lifestyle and frequency of food consumption, among other relevant factors, was obtained by questionnaires administered to the mothers.

RESULTS

Geometric means of serum concentrations (ng/ml) were 0.11 for β-hexachloro-cyclohexane (β-HCH), 0.09 for endosulfan, 0.20 for endosulfan-ether, 0.51 for hexachorobenzene (HCB), 0.08 for mirex, 0.06 for oxychlordane, 0.36 for p,p'-DDE, 0.20 for PCB 138, 0.36 for PCB 153, and 0.45 for PCB 180. Percentage of samples above the limit of detection (0.05 ppb) ranged from 32 (β-HCH) to 100 (HCB). A high variability in OC levels depending on the compound was observed between our results and others found in similar studies carried out in children. Variables related to fish consumption were found to be the major dietary determinant of PCB 138, p,p´-DDE, endosulfan-α, β-HCH, mirex and oxychlordane levels.

CONCLUSIONS

Children participating in this study showed detectable levels of many OC, despite these compounds are no longer used. Their presence in children serum can be explained by their high lipophilicity and environmental persistence, leading to contamination of fatty food. In this line, fish consumption seemed to be the most relevant determinant of OC levels found in our study.

Metal arc welding and the risk of skin cancer

OBJECTIVES

Arc welding produces the full spectrum of ultraviolet radiation and may be a contributory cause of skin cancer; however, there has been little research into this occupational hazard. The aim of this study is to explore if metal arc welding increases the risk of malignant melanoma and/or basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) on skin areas which may possibly be exposed (neck, head, and upper extremities).

METHOD

A Danish national company-based historic cohort of 4333 male metal arc welders was followed from 1987 through 2012 to identify the risk of skin cancer. An external reference group was established including all Danish skilled and unskilled male workers with similar age distribution. Occupational histories were gathered by questionnaires in 1986 and information about skin cancer diagnoses [BCC, SCC, cutaneous malignant melanoma (CMM), and precancerous conditions, actinic keratosis (AK)] were gathered from the Danish Cancer Registry supplemented by the data from the Danish Pathology Register. Hazard ratios (HRs) were calculated in the follow-up period from 1987 until 2012 using Cox regression analysis and adjusted for baseline data regarding age and social group.

RESULTS

The adjusted HR and 95% confidence interval (CI) for skin cancer (all types) were 0.99 (CI 0.94-1.04) for welders. The adjusted HR for AK and BCC located only at neck was 2.49 (CI 1.03-5.99) for welders exposed >20 years (n = 5) and 2.46 (CI 1.02-5.94), respectively, for welders exposed >30 years (n = 5). No statistically significant difference was observed for SCC. The risk of CMM at the neck was also significantly elevated after 30 years of welding, but this is based upon only one exposed case.

CONCLUSION

This study indicates that long-term exposure to metal arc welding may be related to increased risk of BCC and AK located exclusively at the neck. The study provides no support for the hypothesis that welding exposure increases the risk for skin cancer at other locations.

Use of non-prescription analgesics and male reproductive function

We studied the association between intake of non-prescription analgesics and semen quality and male reproductive hormone levels in a cross-sectional study among 1493 men. The men provided one semen (n=1493) and blood sample (n=1056) and filled in questionnaires on use of non-prescription analgesics (paracetamol, NSAIDs and combination drugs (yes/no)). Adjusting for age, study and other covariates, we observed no association between intake of non-prescription analgesics and markers of semen quality. Adjusting for age and time of day of blood sampling, users of non-prescription analgesics had a 10.4% (95% confidence interval (CI) 4.0-17.1%) higher testosterone level than non-users. When we stratified by medication type, the association between analgesics and higher testosterone was observed between users of non-steroidal anti-inflammatory drugs (NSAIDs) and combination drugs but not paracetamol. This study suggests that use of non-prescription analgesics is associated with slightly higher serum testosterone levels than non-use.

Sex Hormones and Semen Quality in Welders Exposed to Hexavalent Chromium

Recent experimental studies in rodents document the spermatotoxic effects of watersoluble hexavalent chromium. Welders comprise, worldwide, a major occupational group with acknowledged exposure to chromium. This study examines the relationship between semen quality and chromium in the urine and blood of a population of 30 tungsten inert gas (TIG) stainless steel welders, 30 mild steel welders and 47 non-welding workers. Each subject provided two to three semen samples. The chromium concentration ranged from 0.17 to 4.74 nmol mmol1 creatinine (median 1.08) in post-shift spot urine and from 6.0 to 46.4 nmol 1-1 in blood. None of several semen parameters deteriorated with increasing level of internal exposure to chromium. Low-level exposure to hexavalent chromium associated with TIG stainless steel and mild steel welding do not appear to be a major hazard for human spermatogenesis.

Sex Hormones and Epididymal Sperm Parameters in Rats Following Sub-chronic Treatment with Hexavalent Chromium

Testicular atrophy and reduced epididymal sperm count are known to occur after i.p. administration of high doses of hexavalent chromium to rats.

The effect of 0.5 mg kg -1 hexavalent chromium injected i.p. 5 d a week for 8 weeks was investigated in male Wistar rats.

A significant reduction in epididymal sperm motility was found at the end of the exposure period. The reduction was reversed after an unexposed period of a further 8 weeks.

In addition, a decrease in serum testosterone and an increase in FSH were found at the end of the exposure period.

The results indicate that a number of mechanisms may be involved in the deleterious effects of chromate on male fecundity.

Risk of depressive disorder following disasters and military deployment: systematic review with meta-analysis

BACKGROUND

Numerous studies describe the occurrence of post-traumatic stress disorder following disasters, but less is known about the risk of major depression.

AIMS

To review the risk of depressive disorder in people surviving disasters and in soldiers returning from military deployment.

METHOD

A systematic literature search combined with reference screening identified 23 controlled epidemiological studies. We used random effects models to compute pooled odds ratios (ORs).

RESULTS

The average OR was significantly elevated following all types of exposures: natural disaster OR = 2.28 (95% CI 1.30-3.98), technological disaster OR = 1.44 (95% CI 1.21-1.70), terrorist acts OR = 1.80 (95% CI 1.38-2.34) and military combat OR = 1.60 (95% CI 1.09-2.35). In a subset of ten high-quality studies OR was 1.41 (95% CI 1.06-1.87).

CONCLUSIONS

Disasters and combat experience substantially increase the risk of depression. Whether psychological trauma per se or bereavement is on the causal path is unresolved.

Prenatal exposure to environmental chemical contaminants and asthma and eczema in school-age children

BACKGROUND

Emerging evidence suggests that prenatal or early-life exposures to environmental contaminants may contribute to an increased risk of asthma and allergies in children. We aimed to the explore associations of prenatal exposures to a large set of environmental chemical contaminants with asthma and eczema in school-age children.

METHODS

We studied 1024 mother-child pairs from Greenland and Ukraine from the INUENDO birth cohort. Data were collected by means of an interview-based questionnaire when the children were 5-9 years of age. Questions from the ISAAC study were used to define asthma, eczema, and wheeze. We applied principal components analysis (PCA) to sixteen contaminants in maternal serum sampled during pregnancy, including perfluoroalkyl substances (PFASs), metabolites of diethylhexyl (DEHP) and diisononyl (DiNP) phthalates, PCB-153, and p,p'-DDE. Scores of five principal components (PCs) explaining 70% of the variance were included in multiple logistic regression models.

RESULTS

In a meta-analysis that included both populations, the PC2 score, reflecting exposure to DiNP, was negatively associated with current eczema (OR 0.71, 95% CI 0.52-0.96). Other associations were not consistent between the two populations. In Ukrainian children, the PC3 score (DEHP) was positively associated with current wheeze (adjusted OR 1.56, 95% CI 1.03-2.37), whereas the PC5 score, dominated by perfluorooctanoic acid (PFOA), was inversely associated with current wheeze (OR 0.64, 0.41-0.99). In Greenlandic children, a negative association of PC4 (organochlorines) with ever eczema (OR 0.78, 0.61-0.99) was found.

CONCLUSIONS

We found limited evidence to support a link between prenatal exposure to environmental chemical contaminants and childhood asthma and eczema.

Psychosocial job strain and risk of congenital malformations in offspring--a Danish National cohort study

OBJECTIVE

To investigate if maternal exposure to psychosocial job strain at work (high demands and low control) measured by questionnaire early in pregnancy (median week 15) is associated with malformations in the offspring.

DESIGN

Population-based cohort study.

SETTING

The Danish National Birth Cohort.

POPULATION

A cohort of 60,386 singleton children with full information on mother's occupational status, exposure to psychosocial job strain and all covariates during pregnancy.

METHODS

Logistic regression analysis was used to calculate the odds of congenital malformations as a function of job strain with adjustment for maternal age, body mass index, parity, smoking, alcohol use, manual versus nonmanual work, maternal serious disease and gestational age at interview.

MAIN OUTCOME MEASURES

Circulatory malformation, musculoskeletal malformation or any malformation.

RESULTS

Logistic regression analyses, both crude and adjusted, indicated no associations between working under high strain and giving birth to a child with circulatory malformation (adjusted odds ratio [OR] 1.04, 95% confidence interval [95% CI] 0.75-1.44), musculoskeletal malformation (aOR 0.88, 95% CI 0.71-1.10) or any malformation (aOR 0.99, 95% CI 0.85-1.15). Supplementary analyses including restriction to first-borns and a stratified analysis with respect to manual and nonmanual work did not change the results.

CONCLUSIONS

Association between exposure to high job strain during pregnancy and elevated risk of circulatory, muscle and any malformations is not supported by this study.

Non-linear association between androgen receptor CAG and GGN repeat lengths and reproductive parameters in fertile European and Inuit men

Recently the dogma that there is an inverse linear association between androgen receptor (AR) CAG and GGN polymorphisms and receptor activity has been challenged. We analysed the pattern of association between 21 male reproductive phenotypes and AR CAG/GGN repeat lengths in 557 proven-fertile men. A linear association was only found between sperm DNA fragmentation index (DFI) and CAG length, and between inhibin B and GGN length. Men with longer CAG then the reference (22-24), had higher oestradiol levels, whereas men with shorter CAG stretches had a higher DFI and a higher proportion of Fas-positive germ cells. Subjects with either short or long CAG had increased seminal levels of prostate-specific antigen and neutral α-glucosidase activity. Compared to men with the median GGN length of 23, those with shorter GGN repeats had higher levels of inhibin B, higher proportions of normal and progressive sperm, and a higher fraction of Fas-positive sperm, while men with longer GGN had higher oestradiol levels. These data indicate that at least for some markers of male reproductive function the association with CAG or GGN repeat length is curvilinear.

BMI in relation to sperm count: an updated systematic review and collaborative meta-analysis

BACKGROUND The global obesity epidemic has paralleled a decrease in semen quality. Yet, the association between obesity and sperm parameters remains controversial. The purpose of this report was to update the evidence on the association between BMI and sperm count through a systematic review with meta-analysis. METHODS A systematic review of available literature (with no language restriction) was performed to investigate the impact of BMI on sperm count. Relevant studies published until June 2012 were identified from a Pubmed and EMBASE search. We also included unpublished data (n = 717 men) obtained from the Infertility Center of Bondy, France. Abstracts of relevant articles were examined and studies that could be included in this review were retrieved. Authors of relevant studies for the meta-analysis were contacted by email and asked to provide standardized data. RESULTS A total of 21 studies were included in the meta-analysis, resulting in a sample of 13 077 men from the general population and attending fertility clinics. Data were stratified according to the total sperm count as normozoospermia, oligozoospermia and azoospermia. Standardized weighted mean differences in sperm concentration did not differ significantly across BMI categories. There was a J-shaped relationship between BMI categories and risk of oligozoospermia or azoospermia. Compared with men of normal weight, the odds ratio (95% confidence interval) for oligozoospermia or azoospermia was 1.15 (0.93-1.43) for underweight, 1.11 (1.01-1.21) for overweight, 1.28 (1.06-1.55) for obese and 2.04 (1.59-2.62) for morbidly obese men. CONCLUSIONS Overweight and obesity were associated with an increased prevalence of azoospermia or oligozoospermia. The main limitation of this report is that studied populations varied, with men recruited from both the general population and infertile couples. Whether weight normalization could improve sperm parameters should be evaluated further.

Male-mediated infertility in sons of building painters and gardeners: a nationwide register-based follow-up study

AIM

To investigate whether sons of gardeners and building painters have increased risk of infertility in comparison with sons of bricklayers, carpenters and electricians.

METHODS

Participants were men born 1965-1984 in Denmark whose fathers the year before birth had worked as gardeners, painters, bricklayers, carpenters or electricians (N=22,978). Cases of infertility were identified by Danish registers, and participants were followed-up for up to 24 years after their 20th birthday.

RESULTS

Sons of gardeners did not have increased risk of infertility. Hazard ratios for sons of painters fluctuated around the null in main analyses but were 1.6 (98% CI: 1.0-2.5) and 1.7 (95% CI: 0.9-3.2) in the subset of participants with smallest risk of paternal exposure misclassification.

CONCLUSIONS

Working as gardener or building painter was not related to increased risk of infertility among the next generation of males in main analyses. However, inherent limitations in data may have attenuated true associations.

Accuracy of cryptorchidism diagnoses and corrective surgical treatment registration in the Danish National Patient Registry

PURPOSE

In recent years several Danish studies of the etiology, time trends and long-term health consequences of cryptorchidism have relied on diagnoses and surgical treatments registered in the National Patient Registry. We evaluated the diagnostic accuracy of these registry data.

MATERIALS AND METHODS

According to the Danish National Patient Registry, 16,168 males were diagnosed with cryptorchidism and 9,244 surgical treatments for cryptorchidism were performed between January 1, 1995 and October 10, 2009. We randomly selected 500 diagnosed cases, of which 284 had been managed surgically. We requested the medical records from the departments making the diagnoses and performing the surgery.

RESULTS

We successfully retrieved medical records for 452 diagnosed cases (90%) and 249 operations (88%). Overall positive predictive value of a registry diagnosis of cryptorchidism was 80% (95% CI 77-84) using the testicular position described by the physician performing the clinical examination as the gold standard. Similarly the positive predictive value of the surgical treatment registration was 99% (95% CI 98-100) using the type of procedure performed.

CONCLUSIONS

The data on cryptorchidism in the Danish National Patient Registry are quite accurate. In etiological research the limited misclassification will in most cases only slightly attenuate estimates of the true relative association. Thus, the registry has the potential to serve as a valuable research tool, although caution should be exercised when studying time trends or geographical differences.

Does last week's alcohol intake affect semen quality or reproductive hormones? A cross-sectional study among healthy young Danish men

The association between last 5 days of alcohol intake, semen quality and reproductive hormones was estimated in this cross-sectional study among 347 men. Conventional semen characteristics, DNA fragmentation index and reproductive hormones (testosterone, estradiol, sex hormone-binding globulin (SHBG), follicle-stimulating hormone (FSH), luteinizing hormone (LH) and inhibin B) were determined. There was a tendency towards lower semen characteristics at higher intake of alcohol past 5 days, albeit with no statistically significant dose-response association. The ratio between free estradiol and free testosterone was higher at higher alcohol intake during the 5 days preceding semen sampling. In conclusion, alcohol intake was associated with impairment of most semen characteristics but without a coherent dose-response pattern. The study indicates an association between recent alcohol intake and a hormonal shift towards higher estradiol/testosterone ratio. The hormonal changes observed may over time, lead to adverse effects on semen quality, but longitudinal studies are needed to study this.

The norepinephrine transporter gene is a candidate gene for panic disorder

Panic disorder (PD) is an anxiety disorder characterized by recurrent panic attacks with a lifetime prevalence of 4.7%. Genetic factors are known to contribute to the development of the disorder. Several lines of evidence point towards a major role of the norepinephrine system in the pathogenesis of PD. The SLC6A2 gene is located on chromosome 16q12.2 and encodes the norepinephrine transporter (NET), responsible for the reuptake of norepinephrine into presynaptic nerve terminals. The aim of the present study was to analyze genetic variants located within the NET gene for association with PD. The case-control sample consisted of 449 patients with PD and 279 ethnically matched controls. All cases fulfilled the ICD-10 diagnostic criteria for PD. Genotyping was performed using the Sequenom platform (Sequenom, Inc, San Diego, USA). To test for allelic and haplotypic association, the PLINK software was used, and COMBASSOC was applied to test for gene-wise association. After quality control 29 single nucleotide polymorphisms (SNPs) spanning the gene-region were successfully analyzed. Seven SNPs located within the 5' end of the gene were significantly associated with PD. Furthermore, the NET gene showed overall evidence for association with the disease (P = 0.000035). In conclusion, the present study indicates that NET could be a susceptibility gene for PD.

Exposure assessment of kneeling work activities among floor layers

The objective of this study was to quantify the proportion of kneeling work activities among floor layers and to assess external knee joint forces in five different kneeling work positions. Thirty-three floor layers were videotaped discontinuously and four floor layers were videotaped continuously for a whole working day. External knee forces were measured in five different kneeling work positions in ten floor layers using Computer Dynography. The study showed that floor layers spent a high percentage of time in knee-straining work positions. Kneeling work tasks, particularly gluing and crawling caused high external knee forces ranging from 0.3 Newton (SD 0.2) times body weight when floor layers were kneeling back on the heels, to 3.5 Newton (SD 0.3) times body weight in the crawling work position. The study highlights the need for prevention by minimizing the amount of kneeling work positions among floor layers.

Semen quality according to prenatal coffee and present caffeine exposure: two decades of follow-up of a pregnancy cohort

BACKGROUND

A few studies have investigated the association between male caffeine consumption in adult life and semen quality with conflicting results, but so far no studies have explored the effect of prenatal coffee exposure. We studied the association between prenatal coffee and current caffeine exposure and semen quality and levels of reproductive hormones.

METHODS

From a Danish pregnancy cohort established in 1984-1987, 347 sons out of 5109 were selected for a follow-up study conducted 2005-2006. Semen and blood samples were analyzed for conventional semen characteristics and reproductive hormones and were related to information on maternal coffee consumption during pregnancy and present caffeine consumption. Data were available for 343 men.

RESULTS

There was a tendency toward decreasing crude median semen volume (P = 0.06) and adjusted mean testosterone (P = 0.06) and inhibin B (P = 0.09) concentrations with increasing maternal coffee consumption during pregnancy. Sons of mothers drinking 4-7 cups/day had lower testosterone levels than sons of mothers drinking 0-3 cups/day (P = 0.04). Current male caffeine intake was associated with increasing testosterone levels (P = 0.007). Men with a high caffeine intake had approximately 14% higher concentration of testosterone than those with a low caffeine intake (P = 0.008).

CONCLUSIONS

The results observed in this study are only tentative, but they do not exclude a small to moderate effect of prenatal coffee exposure on semen volume and levels of reproductive hormones. Present adult caffeine intake did not show any clear associations with semen quality, but high caffeine intake was associated with a higher testosterone concentration.

Parental subfecundity and risk of decreased semen quality in the male offspring: a follow-up study

A few studies have found poor semen quality in sons whose mothers have received fertility treatment, but it is unknown whether the poor semen quality is related to the infertility treatment or to infertility per se, for example, whether it is caused by hereditable factors. Using data from a population-based, Danish follow-up study conducted in 2005-2006, the authors of the present study examined whether sons of subfertile couples who had not received fertility treatment had poorer semen quality than sons of fertile couples. Among the 311 participants, an inverse association between parental waiting time to pregnancy and both semen volume and total sperm count was observed (p trend = 0.04 and p trend = 0.046, respectively). Semen volume in sons of subfertile parents (pregnant after > or =1 years) was 19% lower in comparison with that in sons of parents whose waiting time to pregnancy was 0-6 months (p = 0.02). Additionally, sperm concentration and percentage of morphologically normal sperm were, respectively, 22% (p = 0.15) and 23% (p = 0.13) lower in sons of subfertile parents. Results suggest a small-to-moderate effect of parental subfecundity on semen quality in sons, comparable with the hypothesis that low fecundity has at least partly hereditable causes.

Menstrual cycle characteristics in European and Inuit women exposed to persistent organochlorine pollutants

BACKGROUND

Previous inconsistent results suggest that menstrual cycles may be disturbed by exposure to polychlorinated biphenyls (PCBs) and 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (DDE).

METHODS

Information on menstrual cycle characteristics were obtained by questionnaires, and PCB and DDE were measured in serum samples from a total of 1494 women from Greenland, Swedish fishermen's wives, and inhabitants of Warsaw in Poland and Kharkiv in Ukraine.

RESULTS

No consistent effects of PCB and DDE exposure on menstrual cycle characteristics were observed across populations. Within populations, we observed increased risks of short cycles (< or =24 days) among Swedish fishermen's wives exposed to high levels of PCB [odds ratio (OR) 2.5, confidence interval (CI) 1.2-5.1], and increased risk of long cycles (> or =32 days) among Polish women exposed to high levels of DDE (OR 3.1, CI 1.1-8.6). However, in Greenland it seemed that high levels of PCB or DDE were protective against long menstrual cycles (OR 0.7 CI 0.5-0.96 and OR 0.7 CI 0.5-0.99, respectively).

CONCLUSIONS

It is unlikely that exposure to PCB and DDE is a main cause of menstrual disturbances. Genetic differences or dietary factors may be involved in the non-homogenous associations of organochlorine exposure and menstrual cycle between countries.

Prenatal alcohol exposure and cryptorchidism

AIM

A recently published study reported markedly increased risk of cryptorchidism among boys whose mothers had an average gestational alcohol intake of five or more drinks per week. The aim of this study is to follow up on this finding by estimating the association between prenatal alcohol exposure and persistent cryptorchidism.

METHODS

We used prospectively collected information on prenatal exposures and obstetric information on the birth of 5716 boys, collected from 1984 to 1987. During the 16-19 years of follow-up in a nationwide patient register, 270 cases of cryptorchidism were diagnosed and 185 of these boys underwent orchiopexy.

RESULTS

No positive association between the mothers' average weekly alcohol consumption and persistent cryptorchidism was observed. Binge drinking was nonsignificantly associated with an excess risk of orchiopexy (adjusted RR = 1.4; 95% CI 0.9-2.1), but not with having a diagnosis of cryptorchidism without orchiopexy.

CONCLUSIONS

Mothers' average weekly alcohol intake was not associated with persistent cryptorchidism, but binge drinking may be a risk factor.

Maternal smoking in pregnancy and reproductive hormones in adult sons

Smoking during pregnancy has been reported to alter levels of reproductive hormones in adult sons. From a Danish pregnancy cohort established in 1984-1987, 347 out of 5109 sons were selected according to their exposure to tobacco smoke in foetal life. From February 2005 to January 2006, a blood sample from each young man (18-21 years) was collected and analysed for reproductive hormones. There were no apparent trends of increasing or decreasing hormonal levels with increased exposure to maternal tobacco smoking during pregnancy. Only the free testosterone/free estradiol ratios increased with increased maternal smoking during pregnancy (p for trend = 0.05). No trends for increasing odds ratios for high follicle-stimulating hormone (> or =25 percentile) or low inhibin B (< or =25 percentile) in relation to maternal smoking were observed. We found no major indication of long-term effects of pre-natal exposure to tobacco smoke on the levels of reproductive hormones later in life, but the data may suggest a shift in the hypothalamo-pituitary-gonadal axis towards higher androgenicity. This result was, however, of only borderline significance and could be because of chance.

Is maternal obesity related to semen quality in the male offspring? A pilot study

BACKGROUND

Obesity is a strong predictor of fecundity and maternal obesity may well program semen quality during pregnancy, but to our knowledge, no published studies have evaluated this hypothesis.

METHODS

From a Danish pregnancy cohort established in 1984-87, 347 out of 5109 sons were selected for a follow-up study conducted from February 2005 to January 2006. Semen and blood samples were analyzed for conventional semen characteristics and reproductive hormones and related to information on maternal pre-pregnant body mass index (BMI) that was available for 328 men. Of these, 34 were sons of underweight, and 25 sons of overweight, mothers.

RESULTS

Inhibin B decreased with increasing maternal BMI (P = 0.04) and the point estimates for sperm concentration, semen volume, percent motile sperm, testosterone and FSH suggested an impaired reproductive status among sons of overweight mothers, but none of the trends were statistically significant.

CONCLUSIONS

The results suggest that there may be an effect of high maternal BMI on the sons' semen quality, but the study had only enough power to justify a critical evaluation of the hypothesis in a larger study.

Risk factors for hand-wrist disorders in repetitive work

OBJECTIVES

To identify the risk of hand-wrist disorders related to repetitive movements, use of hand force and wrist position in repetitive monotonous work.

METHODS

Using questionnaires and physical examinations, the prevalence and incidence of hand-wrist pain and possible extensor tendonitis (wrist pain and palpation tenderness) were determined in 3123 employees in 19 industrial settings. With the use of questionnaires and video recordings of homogenous work tasks number of wrist movements, hand force requirements and wrist position were analysed as risk factors for hand-wrist disorders, controlling for potential personal and psychosocial confounders. All participants were re-examined three times during a follow-up period of three years.

RESULTS

Force but not repetition and position was related to hand-wrist pain and possible tendonitis in the baseline analyses showing an exposure-response pattern. Odds ratios for the risk of hand pain was 1.7 (95% CI 1.3 to 2.2) and for possible tendonitis 1.9 (95% CI 1.1 to 3.3). There was no significant interaction between the ergonomic factors. In the follow-up analyses force remained a risk factor for hand pain (OR 1.4, 95% CI 1.1 to 1.8) and for possible tendonitis (OR 2.9, 95% CI 1.3 to 6.8). Repetition was also a risk factor for the onset of hand-wrist pain (OR 1.6, 95% CI 1.2 to 2.3).

CONCLUSIONS

Increasing levels of force were associated with prevalent and incident hand-wrist pain and possible extensor tendonitis. The results for repetition were less consistent. Working with the hand in a non-neutral position could not be identified as a risk factor.

Subfecundity in overweight and obese couples

BACKGROUND

Recent studies indicate that not only women's but also men's obesity has adverse effects on fecundity and since fecundity is a couple concept, we examined fecundity in relation to overweight and obesity of the couple. We also examined the association between weight changes and fecundity over time.

METHODS

Between 1996 and 2002, 64 167 pregnant women enrolled in the Danish National Birth Cohort were interviewed during and 18 months after pregnancy. Information on body mass index (BMI) and waiting time to pregnancy (TTP) was available for 47 835 couples.

RESULTS

Among men and women with a BMI of 18.5 kg/m(2) or more, we found a dose-response relationship between increasing BMI group and subfecundity (a TTP of more than 12 months): Odds ratio (OR) = 1.32 (95% CI: 1.26-1.37) for women and OR = 1.19 (95% CI: 1.14-1.24) for men. Among 2374 women with an initial BMI of 18.5 kg/m(2) or more, who participated more than once in the Danish National Birth Cohort, each kilogram increment in weight between the two pregnancies was associated with a 2.84 (95% CI: 1.33-4.35) days longer TTP.

CONCLUSIONS

Couples have a high risk of being subfecund if they are both obese.

Relationships between sperm DNA fragmentation, sperm apoptotic markers and serum levels of CB-153 and p,p′-DDE in European and Inuit populations

Persistent organochlorine pollutants (POPs) are suspected to interfere with hormone activity and the normal homeostasis of spermatogenesis. We investigated the relationships between sperm DNA fragmentation, apoptotic markers identified on ejaculated spermatozoa and POP levels in the blood of 652 adult males (200 Inuits from Greenland, 166 Swedish, 134 Polish and 152 Ukrainian). Serum levels of 2, 2′, 4, 4′, 5, 5′-hexachlorobiphenyl (CB-153), as a proxy of the total POP burden, and of 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p′-DDE), as a proxy of the total DDT exposure were determined. Sperm DNA fragmentation was measured by using the TUNEL assay, whereas immunofluorescence methods were utilized for detecting pro-apoptotic (Fas) and anti-apoptotic (Bcl-xL) markers. Both TUNEL assay and apoptotic markers were statistically differed across the four populations. No correlation between neither sperm DNA fragmentation nor apoptotic sperm parameters and the large variations in POPs exposure was observed for the separate study groups. However, considering the European populations taken together, we showed that both %TUNEL positivity and Bcl-xL were related to CB-153 serum levels, whereas our study failed to demonstrate any relations between DDE and %TUNEL positivity and apoptotic sperm biomarkers (Fas and Bcl-xL) in any region or overall regions. These results suggest that CB-153 and related chemicals might alter sperm DNA integrity and Bcl-xL levels in European adult males, but not in the highly exposed Inuit men. Additional issues (genetic background, lifestyle habits and characterization of total xeno-hormonal activities) need to be investigated in order to fully assess the population variations observed.

The risk of infertility among hairdressers. Five-year follow-up of female hairdressers in a Danish national registry

BACKGROUND

One in seven married couples is involuntarily infertile. Several chemical exposures in the work environment have been hypothesized to affect female reproduction, and some are present in products used in hairdressing and related trades. Recent Swedish findings indicate that employment in hairdressing poses a risk for female reproductive function. This study examined the possible association between work as a hairdresser and subsequent hospital contact due to female infertility.

METHODS

A cohort of all women in Denmark aged 20-44 years on 1 January 1998 (baseline) and registered as economically active hairdressers, according to national registers, was formed to calculate age-standardized risk ratios (RRs) for hospital contacts due to female infertility during a 5-year follow-up period. Hairdressers were compared to a standard population, that is, all economically active women in Denmark aged 20-44 years at baseline, and to women working as shop assistants.

RESULTS

Sixty-eight cases of hospital contact due to female infertility were observed among the female hairdressers. On the basis of the standard population, the expected number was 73.27, which gives an observed RR of 0.928 (95% CI: 0.72-1.18). Hairdressers and shop assistants exhibited similar rates of hospital contact due to female infertility (1.01; 95% CI: 0.77-1.29).

CONCLUSION

The findings are not corroborating the hypothesis that hairdressers are at increased risk of infertility, but small risks in the entire group or high risks in small subgroups may not be detected by the study.

Is smoking a risk factor for decreased semen quality? A cross-sectional analysis

BACKGROUND

Previous studies suggest a deleterious effect of cigarette smoking on semen quality, but their results have not been consistent. We studied the association between current smoking and semen characteristics and hormonal levels in a large group of healthy men.

METHODS

From 1987 to 2004, seven separate occupational or environmental semen quality studies were co-ordinated by our department. A total of 2562 men participated, each providing semen and blood sample and answering a questionnaire about lifestyle and factors related to health. Appropriate semen and smoking data were available for 2542 men.

RESULTS

Adjusting for study, age and other covariates, we observed an inverse dose-response relation between smoking and semen volume, total sperm count and percentage motile sperm. Heavy smokers had a 19% lower sperm concentration than non-smokers. We found a positive dose-response relationship between smoking and testosterone, LH and the LH/free testosterone ratios.

CONCLUSION

Current smoking in adult life moderately impairs the semen quality. It is well known that semen quality is associated to fecundity. Therefore, it would be sensible to advise men to abstain from smoking to avoid decreased fecundity.