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 We also included unpublished data (n = 717 men) obtained from the Infertility Center of Bondy, France.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.
Combined oral contraceptives (OCs) inhibit ovulation, substantially reduce the volume of menstrual flow and may hypothetically interfere with implantation of refluxed endometrial cells. The aim of ...this review is to establish if OC use influences the risk of endometriosis.
We performed a MEDLINE search to identify all studies published in the last four decades (January 1970 to January 2010) in the English language on the relationship between OC exposure and risk of endometriosis. Two authors abstracted data on standardized forms.
We identified 608 potentially relevant studies and 18 studies (6 cross-sectional, 7 case-control and 5 cohort) were selected. Pooling of the results derived from all the included reports independently from study design, yielded a common relative risk of 0.63 95% confidence interval (CI), 0.47-0.85 for current OC users, 1.21 (95% CI, 0.94-1.56) for past users and 1.19 (95% CI, 0.89-1.60) for ever users. Methodological drawbacks, such as uncertain temporal relationship between exposure and outcome in cross-sectional studies and suboptimal selection of controls in case-control studies, limit the quality of the available evidence.
The risk of endometriosis appears reduced during OC use. However, it is not possible to exclude the possibility that the apparent protective effect of OC against endometriosis is the result of postponement of surgical evaluation due to temporary suppression of pain symptoms. Confounding by selection and indication biases may explain the trend towards an increase in risk of endometriosis observed after discontinuation, but further clarification is needed. To date, the hypothesis of recommending OCs for primary prevention of endometriosis does not seem sufficiently substantiated.
Dampness and visible mold in homes are associated with asthma development, but causal mechanisms remain unclear. The goal of this research was to explore associations among measured dampness, fungal ...exposure, and childhood asthma development without the bias of culture‐based microbial analysis. In the low‐income, Latino CHAMACOS birth cohort, house dust was collected at age 12 months, and asthma status was determined at age 7 years. The current analysis included 13 asthma cases and 28 controls. Next‐generation DNA sequencing methods quantified fungal taxa and diversity. Lower fungal diversity (number of fungal operational taxonomic units) was significantly associated with increased risk of asthma development: unadjusted odds ratio (OR) 4.80 (95% confidence interval (CI) 1.04–22.1). Control for potential confounders strengthened this relationship. Decreased diversity within the genus Cryptococcus was significantly associated with increased asthma risk (OR 21.0, 95% CI 2.16–204). No fungal taxon (species, genus, class) was significantly positively associated with asthma development, and one was significantly negatively associated. Elevated moisture was associated with increased fungal diversity, and moisture/mold indicators were associated with four fungal taxa. Next‐generation DNA sequencing provided comprehensive estimates of fungal identity and diversity, demonstrating significant associations between low fungal diversity and childhood asthma development in this community.
Organophosphosphorus pesticides (OPs) are widely used as insecticides in agriculture. Human exposure to OPs has been linked to adverse effects including poorer child neurodevelopment, reduced birth ...weight, altered serum hormone levels, and reduced semen quality. We measured six OP dialkyl phosphate (DAP) metabolites three dimethyl alkylphosphates (DMs) and three diethyl alkylphosphates (DEs) in urine samples collected two times during pregnancy (~13 and ~26 weeks gestation) from 594 women participating in the CHAMACOS birth cohort study and resided in an agricultural community in the United States (U.S.) between 1999 and 2000. Previous studies have shown these women have higher OP exposures compared with the general U.S. population. We examined bivariate associations between prenatal DAP metabolite levels and exposure determinants such as age, season, years living in the US, housing characteristics, fruit and vegetable consumption, occupation and residential proximity to agricultural fields. Final multivariable models indicated that season of urine collection was significantly associated (p < 0.01) with specific gravity-adjusted DM, DE and total DAP metabolites; samples collected in fall and winter had higher concentrations than those collected in spring-summer. Specific gravity-adjusted levels of DM and total DAP metabolites were significantly higher in women who had resided in the U.S. for 5 years or less (p < 0.05). Levels of DM metabolites also increased with daily fruit and vegetable servings (p < 0.01), and levels of DE metabolites were higher in residences with poorer housekeeping quality (p < 0.01) and in mothers that worked in agriculture (p < 0.05). These findings suggest that there are multiple determinants of OP exposure in pregnant women.
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•Organophosphorus pesticides are widely used as insecticides in a agriculture.•We measured DAP metabolites in pregnant women from an agricultural community.•Years living close to the fields and fruit intake were positively associated with urinary DAPs.•Vegetable washing and housekeeping quality were also related to DAP concentrations.•Behavioral changes can lower the DAPs body burden of exposed individuals.
This study compares the relative effects of advancing male age on multiple genomic defects in human sperm DNA fragmentation index (DFI), chromatin integrity, gene mutations, and numerical chromosomal ...abnormalities, characterizes the relationships among these defects and with semen quality, and estimates the incidence of susceptible individuals for a well characterized nonclinical nonsmoking group of 97 men (22-80 years). Adjusting for confounders, we found major associations between age and the frequencies of sperm with DFI and fibroblast growth factor receptor 3 gene (FGFR3) mutations associated with achondroplasia (P < 0.01) with no evidence for age thresholds. However, we found no associations between age and the frequencies of sperm with immature chromatin, aneuploidies/diploidies, FGFR2 mutations (Apert syndrome), or sex ratio in this cohort. There were also no consistent correlations among genomic and semen-quality endpoints, except between DFI and sperm motility (r = -0.65, P < 0.001). These findings suggest there are multiple spermatogenic targets for genomically defective sperm with substantially variable susceptibilities to age. Our findings predict that as healthy males age, they have decreased pregnancy success with trends beginning in their early reproductive years, increased risk for producing offspring with achondroplasia mutations, and risk of fathering offspring with Apert syndrome that may vary across cohorts, but with no increased risk for fathering aneuploid offspring (Down, Klinefelter, Turner, triple X, and XYY syndromes) or triploid embryos. Our findings also suggest that the burden of genomic damage in sperm cannot be inferred from semen quality, and that a small fraction of men are at increased risk for transmitting multiple genetic and chromosomal defects.
The human secondary sex ratio reportedly falls in populations subjected to exogenous stressors such as earthquakes or political and social upheavals. Explanations of the association include reduced ...conception of males and increased fetal deaths among males. The latter explanation has been supported by research reporting that the sex ratio in California fell 3 months, but not 8, 9 or 10 months, after the terrorist attacks of September 11, 2001. California’s distance from the attacks raises the questions of whether the results arose from chance and would be found elsewhere. We contribute to the literature by testing the association between the secondary sex ratio and the events of September 11 in New York City. METHODS: We replicate the California tests by applying interrupted time-series methods, which control for secular trends, seasonality and other forms of autocorrelation, to 91 cohorts born in New York City during 28-day periods from January 1996 to June 2002. RESULTS: As hypothesized, the sex ratio in New York City in the period 1 January to 28 January 2002 fell to 1, which was the lowest observed value during the test period and significantly (i.e. P < 0.01, two-tailed test) below the value expected from history. CONCLUSIONS: Our findings support the male fetal loss explanation of the association between exogenous population shocks and the secondary sex ratio.
The trend for men to have children at older age raises concerns that advancing age may increase the production of genetically defective sperm, increasing the risks of transmitting germ-line ...mutations. METHODS: We investigated the associations between male age and sperm DNA damage and the influence of several lifestyle factors in a healthy non-clinical group of 80 non-smokers (mean age: 46.4 years, range: 22–80 years) with no known fertility problems using the sperm Comet analyses. RESULTS: The average percentage of DNA that migrated out of the sperm nucleus under alkaline electrophoresis increased with age (0.18% per year, P = 0.006), but there was no age association for damage measured under neutral conditions (P = 0.7). Men who consumed >3 cups coffee per day had ∼20% higher percentage tail DNA under neutral but not alkaline conditions compared with men who consumed no caffeine (P = 0.005). CONCLUSIONS: Our findings indicate that (i) older men have increased sperm DNA damage associated with alkali-labile sites or single-strand DNA breaks and (ii) independent of age, men with substantial daily caffeine consumption have increased sperm DNA damage associated with double-strand DNA breaks. DNA damage in sperm can be converted to chromosomal aberrations and gene mutations after fertilization, increasing the risks of developmental defects and genetic diseases among offspring.
In this study, the authors' objective was to determine whether serum concentrations of polychlorinated biphenyls (PCBs), hexachlorobenzene, p,p′-dichlorodiphenyl trichloroethane (DDT), o,p′-DDT, and ...p,p′-dichlorodiphenyl dichloroethylene (DDE) are associated with thyroid function during pregnancy. These compounds, as well as thyroid-stimulating hormone, total thyroxine, and free thyroxine, were measured in serum samples collected between October 1999 and October 2000 from 334 pregnant women living in the Salinas Valley, California. Data were analyzed by multivariate linear regression. After adjustment for covariates, seven of the 19 PCB congeners detected in more than 75% of participants and the sum of those congeners were negatively associated with free thyroxine concentrations. PCBs 44, 52, and 183 remained significant after the exclusion of two outliers. Hexachlorobenzene concentrations were negatively associated with both free thyroxine and total thyroxine. PCB and hexachlorobenzene concentrations were strongly correlated, which hampered the authors' ability to identify their independent associations with thyroid function. None of the exposures under study were associated with thyroid-stimulating hormone. Results suggest that exposure to PCBs and/or hexachlorobenzene at background levels may affect thyroid function during pregnancy. These findings are of particular significance, since thyroid hormones of maternal origin may play an essential role in fetal neurodevelopment.
BACKGROUND: Although the effect of maternal age on fertility is well known, it is unclear whether paternal age also affects fertility. This cross‐sectional study sought to characterize the ...association between age and semen quality, a well‐known proxy of fertility status. METHODS: A convenience sample of 97 non‐smoking men (aged 22–80 years) without known fertility problems was recruited from a national government laboratory. The men provided semen samples and information relating to lifestyle, diet, medical and occupational details. Semen volume (ml), sperm concentration (×106/ml), total sperm count (×106), motility (%), progressive motility (%) and total progressively motile sperm count (×106) were measured. RESULTS: After adjusting for covariates, semen volume decreased by 0.03 ml per year of age (95% CI: –0.05, –0.01); motility decreased by 0.7% per year (95% CI: –0.92, –0.43); progressive motility decreased by 3.1% per year (95% CI: –4.5, –1.6); and total progressively motile sperm count decreased by 4.7% per year (95% CI: –7.2, –2.2). There was a suggested decrease in sperm concentration and count. The proportion of men with abnormal volume, concentration and motility was significantly increased across the age decades. CONCLUSIONS: In a convenience sample of healthy men from a non‐clinical setting, semen volume and sperm motility decreased continuously between 22–80 years of age, with no evidence of a threshold.
On July 10, 1976, an explosion at a chemical plant in Seveso, Italy, released up to 30kg of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)—the most potent dioxin congener. Twenty years later, the Seveso ...Women's Health Study (SWHS) initiated a follow-up assessment of a cohort of female Seveso residents. Researchers collected serial blood, measured for TCDD levels, and recorded information about the women's medical history after the explosion. The study's aims were to: 1) modify the human PBPK model for TCDD (Emond et al. 2004; Emond et al. 2005; NCEA-USEPA, 2010) to include repetitive gestation and lactation; 2) simulate TCDD blood concentrations during different life stages including pregnancy and lactation, under different exposure scenarios; and 3) use this PBPK model to compare the influence of gestation and lactation on elimination of TCDD. After optimization of the model, it was assessed using data from the SWHS cohort. The 23 women in Subcohort A, were 4–39years old and in Subcohort B, the 18 women were 3–17years old when the explosion occurred. The model accurately predicted the blood concentrations during the 20years post-exposure, including periods of pregnancy and lactation. The model was also used to analyze the contribution of gestation and lactation to the mother's elimination of TCDD. The results suggest that gestation and lactation do not significantly impact TCDD blood elimination. Future efforts will focus on using additional data to evaluate the PBPK model and improving the mathematical descriptions of lactation and multiple gestations.
•PBPK modeling can help to determine what influence the TCDD elimination.•The PBPK model accurately reproduces the exposure profiles of the Seveso women.•A small impact for the mother, but significant ones for the fetus and newborn.•The importance of gestation/lactation was overrated in the old literature of TCDD.•The PBPK model is an important quantification tool for human risk assessments.
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