Despite a century of research on complex traits in humans, the relative importance and specific nature of the influences of genes and environment on human traits remain controversial. We report a meta-analysis of twin correlations and reported variance components for 17,804 traits from 2,748 publications including 14,558,903 partly dependent twin pairs, virtually all published twin studies of complex traits. Estimates of heritability cluster strongly within functional domains, and across all traits the reported heritability is 49%. For a majority (69%) of traits, the observed twin correlations are consistent with a simple and parsimonious model where twin resemblance is solely due to additive genetic variation. The data are inconsistent with substantial influences from shared environment or non-additive genetic variation. This study provides the most comprehensive analysis of the causes of individual differences in human traits thus far and will guide future gene-mapping efforts. All the results can be visualized using the MaTCH webtool.
PMID 25985137 25985137 DOI 10.1038/ng.3285 10.1038/ng.3285 Polderman et al. 2015, Polderman 2015
Cite this article
Polderman, T. J., Benyamin, B., de Leeuw, C. A., Sullivan, P. F., van Bochoven, A., Visscher, P. M., & Posthuma, D. (2015). Meta-analysis of the heritability of human traits based on fifty years of twin studies. Nat Genet. https://doi.org/10.1038/ng.3285
Polderman TJ, Benyamin B, de Leeuw CA, Sullivan PF, van Bochoven A, Visscher PM, Posthuma D. Meta-analysis of the heritability of human traits based on fifty years of twin studies. Nat Genet. 2015. doi:10.1038/ng.3285
Polderman, T. J., et al. "Meta-analysis of the heritability of human traits based on fifty years of twin studies." Nat Genet, 2015.
Adolescent heavy menstrual bleeding(HMB), menorrhagia or abnormal uterine bleeding commonly occur in adolescent women. The differential diagnosis can be challenging. The pneumonic: PALM-COEIN (polyp, adenomyosis, leiomyoma, malignancy and hyperplasia, coagulopathy, ovulatory dysfunction, endometrial, iatrogenic, and not yet classified), is commonly used but it does not stratify as to the likelihood of a disorder. We have sought to develop a probability-based differential diagnosis for Adolescent HMB, menorrhagia or abnormal uterine bleeding. A comprehensive literature search was conducted using PubMed, EMBASE, and SCOPUS databases. Case series describing adolescents from 10-19 years of age with HMB, menorrhagia or abnormal uterine bleeding was acceptable if: more than 10 patients were included; editorials, case reports, and secondary sources such as review articles, or book chapters were excluded. No language filter was used, but an English abstract was required. The etiology of HMB, menorrhagia or abnormal uterine bleeding, and the country of origin was extracted from articles that met inclusion criteria. Cumulative rate estimates were determined by Bayesian probability modeling. Seventeen full text articles were reviewed in detail; 2,770 patients were included. The most frequent causes of HMB were Ovarian Uterine Disorders (23.7%; 95% CredI 22-25.5%), Coagulation Disorders (19.4%; 95% CredI 17.8-21.1%), and Platelet Disorders (6.23%; 95% CredI 5.27-7.27%) with 45.9% (95% CredI 43.8-47.%9) of the cases of indeterminate origin. The leading causes of HMB in healthy adolescent females were varied. The sub-analysis identified distinct etiologies, suggesting that multiple factors must be considered in the evaluation of HMB. While PALM-COEIN (polyp, adenomyosis, leiomyoma, malignancy and hyperplasia, coagulopathy, ovulatory dysfunction, endometrial, iatrogenic, and not yet classified) provides us with a comprehensive picture of the possible causes of HMB in females, this systematic review assigns probabilities to the etiologies of HMB in adolescent females, providing physicians with a more focused and efficient pathway to diagnosis.
Impaired vitamin D status is highly prevalent among women with UFs. The objective of this first-ever systematic review and meta-analysis was to summarize the effect of vitamin D supplementation on the size of uterine fibroids (UFs). We performed a comprehensive literature search for published randomized controlled trials (RCTs) in Medline, Scopus, Web of Science, and Cochrane Central Register of Controlled Trials from inception to September 2022. Five trials including 511 participants (256 cases and 255 controls) were included. Pooling results from five trials, which compared size of UFs between experimental and placebo groups, revealed that vitamin D supplementation could significantly decrease the size of UFs (standardized mean difference [SMD]: -0.48, 95% confidence interval [CI]: -0.66, -0.31) and cause improvement in serum level of vitamin D compared to placebo group (SMD: 3.1, 95% CI: 0.66, 5.55). A significant effect was observed in the subset of trials administering vitamin D supplementation for >8 wk (SMD: -0.62, 95% CI: -0.88, -0.37). In conclusion, vitamin D supplementation significantly increases serum levels of vitamin D and reduces the size of UFs. However, larger, well-designed RCTs are still needed to determine the effect of vitamin D on other parameters of UFs.
The evidence on the association between diet and miscarriage risk is scant and conflicting. To summarize the evidence on the association between periconceptual diet and miscarriage risk in healthy women of reproductive age. Data Sources: Electronic databases were searched from inception to August 2022 without restriction of regions, publication types, or languages. Experimental or observational studies were considered for inclusion. The population was healthy women of reproductive age. Exposure was periconception diet. Study quality was assessed using the modified Newcastle-Ottawa Scale. Summary effect sizes (odds ratio [OR] with 95% confidence interval [CI]) were calculated for each food category. Outcomes: Miscarriage rate (as defined by primary studies). We included 20 studies (11 cohort and 9 case-control), of which 6 presented data suitable for meta-analysis (2 cohort and 4 case-control, n = 13,183 women). Our primary analyses suggest a reduction in miscarriage odds with high intake of the following food groups: fruit (OR, 0.39; 95% CI, 0.33-0.46), vegetables (OR, 0.59; 95% CI, 0.46-0.76), fruit and vegetables (OR, 0.63; 95% CI, 0.50-0.81), seafood (OR, 0.81; 95% CI, 0.71-0.92), dairy products (OR, 0.63; 95% CI, 0.54-0.73), eggs (OR, 0.81; 95% CI, 0.72-0.90), and cereal (grains) (OR, 0.67; 95% CI, 0.52-0.87). The evidence was uncertain for meat, red meat, white meat, fat and oil, and sugar substitutes. We did not find evidence of an association between adherence to predefined dietary patterns and miscarriage risk. However, a whole diet containing healthy foods as perceived by the trialists, or with a high Dietary Antioxidant Index score (OR, 0.43; 95% CI, 0.20-0.91) may be associated with a reduction in miscarriage risk. In contrast, a diet rich in processed food was demonstrated to be associated with increased miscarriage risk (OR, 1.97; 95% CI, 1.36-3.34). A diet abundant in fruit, vegetables, seafood, dairy, eggs, and grain may be associated with lower miscarriage odds. Further interventional studies are required to accurately assess the effectiveness of periconception dietary modifications on miscarriage risk. PROSPERO Registration: CRD42020218133.
McNulty KL et al., 2020·Sports medicine (Auckland, N.Z.)
Concentrations of endogenous sex hormones fluctuate across the menstrual cycle (MC), which could have implications for exercise performance in women. At present, data are conflicting, with no consensus on whether exercise performance is affected by MC phase. To determine the effects of the MC on exercise performance and provide evidence-based, practical, performance recommendations to eumenorrheic women. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Four databases were searched for published experimental studies that investigated the effects of the MC on exercise performance, which included at least one outcome measure taken in two or more defined MC phases. All data were meta-analysed using multilevel models grounded in Bayesian principles. The initial meta-analysis pooled pairwise effect sizes comparing exercise performance during the early follicular phase with all other phases (late follicular, ovulation, early luteal, mid-luteal and late luteal) amalgamated. A more comprehensive analysis was then conducted, comparing exercise performance between all phases with direct and indirect pairwise effect sizes through a network meta-analysis. Results from the network meta-analysis were summarised by calculating the Surface Under the Cumulative Ranking curve (SUCRA). Study quality was assessed using a modified Downs and Black checklist and a strategy based on the recommendations of the Grading of Recommendations Assessment Development and Evaluation (GRADE) working group. Of the 78 included studies, data from 51 studies were eligible for inclusion in the initial pairwise meta-analysis. The three-level hierarchical model indicated a trivial effect for both endurance- and strength-based outcomes, with reduced exercise performance observed in the early follicular phase of the MC, based on the median pooled effect size (ES0.5 = - 0.06 [95% credible interval (CrI): - 0.16 to 0.04]). Seventy-three studies had enough data to be included in the network meta-analysis. The largest effect was identified between the early follicular and the late follicular phases of the MC (ES0.5 = - 0.14 [95% CrI: - 0.26 to - 0.03]). The lowest SUCRA value, which represents the likelihood that exercise performance is poor, or among the poorest, relative to other MC phases, was obtained for the early follicular phase (30%), with values for all other phases ranging between 53 and 55%. The quality of evidence for this review was classified as "low" (42%). The results from this systematic review and meta-analysis indicate that exercise performance might be trivially reduced during the early follicular phase of the MC, compared to all other phases. Due to the trivial effect size, the large between-study variation and the number of poor-quality studies included in this review, general guidelines on exercise performance across the MC cannot be formed; rather, it is recommended that a personalised approach should be taken based on each individual's response to exercise performance across the MC.