In a recent study researchers investigated the impacts of multiple metal exposure on female fertility. They used a nested case-control study comprising 180 participants and multiple regression models for their analyses. Their findings reveal that, out of the 22 metals analyzed, eight metals (especially Copper and Chromium) were found to have adverse effects on fertility. At the same time, Zinc was observed to exert a protective effect in the association. These findings form the basis for future research that may identify novel interventions in the battle against globally declining fertility rates.
Study
In the present study, researchers used ICP-MS to evaluate the plasma concentrations and relative contributions of 22 metals to female fertility, identify the ones with the greatest impacts, and elucidate any synergistic interactions between different metal elements. The study cohort was derived from the Free Pre-pregnancy Health Examination Project carried out by the Maternal and Child Center of Gulou District, Nanjing, Jiangsu Province, China. Study inclusion criteria comprised age (20, the legal Chinese marriage age for women) and consent to pregnancy (provided by both spouses). Exclusion criteria included pregnancy at baseline (pre-pregnancy) checkup, diagnoses of infertility, genetic deformations, or sexually transmitted infections (STIs) in either spouse.
Four hundred and fifty-four individuals met the study inclusion criteria and were recruited into the research, with follow-ups every three months up to a duration of one year. Of these, 214 women became pregnant over the year-long duration. Participants were subsequently divided into a nest case-control study design comprising a pregnancy group (cases; n = 90) and a non-pregnancy group (controls; n = 90).
Data collection was obtained by conducting a baseline epidemiological survey of included participants. Collected data included age (including age difference between spouses), occupation, education, and pregnancy history. For the purposes of this study, fertility was defined solely as the ability to become pregnant, and successful delivery was not included as a requirement. Participant-provided plasma samples were used for metal concentration measurements of 22 common metal pollutants, obtained using a quadrupole inductively coupled plasma mass spectrometer (ICP-MS, BRUKER AURORA M90, Analytik Jena, Germany).
Metals screened in this study – “Lithium (Li), Natrium (Na), Magnesium (Mg), Aluminium (Al), Calcium (Ca), Titanium (Ti), Chromium (Cr), Manganese (Mn), Cobalt (Co), Nickel (Ni), Copper (Cu), Zinc (Zn), Gallium (Ga), Selenium (Se), Rubidium (Rb), Strontium (Sr), Zirconium (Zr), Molybdenum (Mo), Cesium (Cs), Barium (Ba), Thallium (Tl), and Lead (Pb)”
Statistical analyses included t-tests or the Kruskal-Wallis tests to assess continuous variable differences between groups. Similarly, the chi-squared test or Fisher’s exact probability test was used for classification variables. The least absolute shrinkage and selection operator (LASSO) penalty regression analysis was used to identify the metals contributing most significantly to observed fertility trends. The Bayesian kernel machine regression (BKMR) model was used to elucidate the combination effects of multiple metals on female health (fertility).
Results and Conclusion
Demographic data revealed a slight yet statistically significant difference between the mean ages of the case and control cohorts – 28.5 and 29.8 years, respectively. Education level was found to play a role in fertility, with a higher education level corresponding to improved fertility outcomes.
LASSO analyses revealed eight metals found to exert significant influence on female fertility, namely, Ca, Co, Cr, Cu, Rb, Zn, Sr, and Zr. Uncorrected logistic regression models revealed that Cr, Cu, Co, and Rb were negatively associated with fertility, while Zn was found to improve fertility outcomes. After correcting for demographic covariates and confounding factors, logistic regressions show that Cu and Co remain significant (negative association), as does Zn (positive association). While not substantial at recorded plasma concentrations, at higher doses, Cr and Rb were found to be closely associated with reduced female fertility.
When estimating the mixed/synergistic effects of metals in combination, Zn, Ca, and Zr showed a positive correlation with fertility, while Cr, Co, Rb, and Cu displayed a negative correlation.
In summary, this study reveals that Cu, Cr, Rb, and Co are associated with adverse fertility outcomes, and their environmental contamination may play a critical role in globally reducing fertility rates. In contrast, Zn was found to have a protective effect and improve fertility rates (in moderate concentrations). Cu, Cr, and Rb might show synergistic effects stronger than their individual contributions.
Source:
https://www.news-medical.net/news/20240207/Metal-pollution-contributes-to-reduced-female-fertility-with-Zinc-as-a-notable-exception.aspx