Dietary phytoestrogen intake and ovarian cancer risk: a prospective study in the Prostate, Lung, Colorectal and Ovarian (PLCO) cohort.

Estrogen plays crucial roles in ovarian tumorigenesis. Phytoestrogens (PEs) are a type of daily dietary nutrients for humans and possess a mild estrogenic characteristic. This study aimed to assess the correlation of the consumption of dietary PEs with ovarian cancer risk using data in the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial. Participants were enrolled in PLCO from 1993 to 2001. Hazard ratios (HRs) and 95% confidence intervals (CIs) were utilized to determine the association between the intake of PEs and ovarian cancer occurrence, which were calculated by the Cox proportional hazards regression analysis. Totally, 24,875 participants were identified upon completion of the initial dietary questionnaire (DQX). Furthermore, the analysis also included a total of 45,472 women who filled out the diet history questionnaire (DHQ). Overall, after adjustment for confounders, the dietary intake of total PEs was significantly associated with the risk of ovarian cancer in the DHQ group (HRQ4vsQ1 = 0.69, 95% CI: 0.50-0.95; P for trend = 0.066). Especially, individuals who consumed the highest quartile of isoflavones were found to have a decreased risk of ovarian cancer in the DHQ group (HRQ4vsQ1 = 0.68, 95% CI: 0.50-0.94; P for trend = 0.032). However, no such significant associations were observed for the DQX group. In summary, this study suggests that increased dietary intake of total PEs especially isoflavones was linked with a lower risk for developing ovarian cancer. More researches are necessary to validate the findings and explore the potential mechanisms.

Genetically predicted selenium concentrations and thyroid function: A two-sample Mendelian randomization study.

OBJECTIVE: The impact of selenium (Se) on human thyroid function remains unclear, with inconsistent results from recent epidemiological studies. Moreover, the observed associations are prone to bias due to potential confounding and reverse causation. Mendelian randomization (MR) analysis facilitates the large minimization of biases produced by environmental and lifestyle influences, providing unconfounded estimates of causal effects using instrumental variables. We aim to examine the association between Se concentrations and human thyroid function using a two-sample MR analysis. DESIGN AND METHODS: Genetic instruments for Se concentrations, including toenail and blood (TAB) and blood Se concentrations, were identified from a genome-wide association study (GWAS) of blood Se (n = 5477) and toenail Se levels (n = 4162). GWAS summary statistics on thyroid phenotypes were downloaded from the ThyroidOmics consortium, including thyroid-stimulating hormone (TSH) (n = 54,288), free thyroxin (FT4) (n = 49,269), hypo (n = 53,423), and hyperthyroidism (n = 51,823). The MR study was conducted using the inverse-variance weighted (IVW) method, supplemented with the weighted median and the mode-based method. RESULTS: Genetically determined TAB Se was negatively associated with FT4 (ß = -.067; 95% confidence interval [CI] = -0.106, -0.028; p = 0.001) using the IVW analyses, as well in the additional analyses using the weighted median and weighted-mode methods. No evidence in heterogeneity, pleiotropy or outlier single-nucleotide polymorphisms was detected (all p > 0.05). Suggestive casual association between increased genetically determined TAB Se concentrations and decreased hypothyroidism risk was found by the IVW method (odds ratio [OR] = 0.847; 95% CI = 0.728, 0.985; p = 0.031). The causal effect of TAB Se on FT4 was observed in women (ß = -.076; 95% CI = -0.129, -0.024; p = 0.004). However, the influence of genetically determined higher Se concentrations on TSH levels and hyperthyroidism revealed insignificance in the primary and sensitivity analyses. CONCLUSIONS: The present MR study indicated that high Se concentration enable the decreasing of FT4 levels, and the effects of Se concentrations on FT4 remain sex-specific.

Educational attainment and offspring birth weight: A bidirectional Mendelian randomization study.

Background: The association between educational attainment (EA) and offspring birth weight (BW) has been reported by several traditional epidemiological studies. However, evidence for this association tends to be mixed and confounded. This study aimed to investigate the causal association between EA of parents and offspring BW. Methods: Here, we carried out a two-sample bidirectional Mendelian randomization (MR) analysis to examine the causal association between EA of males (n = 131,695) and females (n = 162,028) and offspring BW using genetic instruments. Summary statistics of EA associated single nucleotide polymorphisms (SNPs) were extracted from a GWAS incorporating 293,723 individuals of European descent performed by the Social Science Genetic Association Consortium (SSGAC), and the effects of these SNPs on offspring BW were estimated using a GWAS meta-analysis of 86,577 participants of European descent from 25 studies. Univariable MR analyses were conducted using the inverse-variance weighted (IVW) method and four other methods. Further sensitivity analyses were carried out to test the viability of the results. Multivariable MR was used to examine the confounders between the exposure and outcome. Results: The result shows evidence that the offspring BW is positively causally affected by female EA. Each one standard deviation (SD) increase in female EA was associated with 0.24 SD higher of offspring BW (95% confidence interval [CI], 0.10 to 0.37, p < 0.001 for the IVW method). Similarly, change in offspring BW was 0.21 SD (95% CI: 0.07 to 0.34, p = 2.82 × 10-3) per one SD higher in male EA. No causal effect of BW on EA was found by any of the five methods. The causal association between female EA and offspring BW maintained after adjusting for alcoholic drinks per week and BMI. The effect of male EA on offspring BW was attenuated when we adjusted for BMI and alcoholic drinks per week using multivariable MR analysis. Conclusion: Our study indicated that female EA is positively causally associated with offspring BW. The association between male EA and offspring BW may be confounded by alcoholic drinks per week and BMI.