scholarly journals Consistent Estimation in Mendelian Randomization with Some Invalid Instruments Using a Weighted Median Estimator

2016 ◽  
Vol 40 (4) ◽  
pp. 304-314 ◽  
Author(s):  
Jack Bowden ◽  
George Davey Smith ◽  
Philip C. Haycock ◽  
Stephen Burgess
Keyword(s):  
Mendelian Randomization ◽  
Consistent Estimation ◽  
Invalid Instruments ◽  
Weighted Median

Life Course Adiposity and Alzheimer’s Disease: A Mendelian Randomization Study

2021 ◽  
pp. 1-10
Author(s):  
Xian Li ◽  
Yan Tian ◽  
Yu-Xiang Yang ◽  
Ya-Hui Ma ◽  
Xue-Ning Shen ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Life Course ◽  
Mendelian Randomization ◽  
Association Studies ◽  
Meta Analysis ◽  
Genome Wide Association Studies ◽  
Fat Percentage ◽  
Regression Methods ◽  
Weighted Median

Background: Several studies showed that life course adiposity was associated with Alzheimer’s disease (AD). However, the underlying causality remains unclear. Objective: We aimed to examine the causal relationship between life course adiposity and AD using Mendelian randomization (MR) analysis. Methods: Instrumental variants were obtained from large genome-wide association studies (GWAS) for life course adiposity, including birth weight (BW), childhood body mass index (BMI), adult BMI, waist circumference (WC), waist-to-hip ratio (WHR), and body fat percentage (BFP). A meta-analysis of GWAS for AD including 71,880 cases and 383,378 controls was used in this study. MR analyses were performed using inverse variance weighted (IVW), weighted median, and MR-Egger regression methods. We calculated odds ratios (ORs) per genetically predicted standard deviation (1-SD) unit increase in each trait for AD. Results: Genetically predicted 1-SD increase in adult BMI was significantly associated with higher risk of AD (IVW: OR = 1.03, 95% confidence interval [CI] = 1.01–1.05, p = 2.7×10–3) after Bonferroni correction. The weighted median method indicated a significant association between BW and AD (OR = 0.94, 95% CI = 0.90–0.98, p = 1.8×10–3). We also found suggestive associations of AD with WC (IVW: OR = 1.03, 95% CI = 1.00–1.07, p = 0.048) and WHR (weighted median: OR = 1.04, 95% CI = 1.00–1.07, p = 0.029). No association was detected of AD with childhood BMI and BFP. Conclusion: Our study demonstrated that lower BW and higher adult BMI had causal effects on increased AD risk.

scholarly journals A Mendelian randomization analysis of the relationship between cardioembolic risk factors and ischemic stroke

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Danyang Tian ◽  
Linjing Zhang ◽  
Zhenhuang Zhuang ◽  
Tao Huang ◽  
Dongsheng Fan
Keyword(s):  
Risk Factors ◽  
Ischemic Stroke ◽  
Mendelian Randomization ◽  
P Wave ◽  
Cardioembolic Stroke ◽  
Large Artery ◽  
Weighted Analysis ◽  
Inverse Variance ◽  
Weighted Median ◽  
Genetically Determined

AbstractObservational studies have shown that several risk factors are associated with cardioembolic stroke. However, whether such associations reflect causality remains unknown. We aimed to determine whether established and provisional cardioembolic risk factors are causally associated with cardioembolic stroke. Genetic instruments for atrial fibrillation (AF), myocardial infarction (MI), electrocardiogram (ECG) indices and N-terminal pro-brain natriuretic peptide (NT-pro BNP) were obtained from large genetic consortiums. Summarized data of ischemic stroke and its subtypes were extracted from the MEGASTROKE consortium. Causal estimates were calculated by applying inverse-variance weighted analysis, weighted median analysis, simple median analysis and Mendelian randomization (MR)-Egger regression. Genetically predicted AF was significantly associated with higher odds of ischemic stroke (odds ratio (OR): 1.20, 95% confidence intervals (CI): 1.16–1.24, P = 6.53 × 10–30) and cardioembolic stroke (OR: 1.95, 95% CI: 1.85–2.06, P = 8.81 × 10–125). Suggestive associations were found between genetically determined resting heart rate and higher odds of ischemic stroke (OR: 1.01, 95% CI: 1.00–1.02, P = 0.005), large-artery atherosclerotic stroke (OR: 1.02, 95% CI: 1.00–1.04, P = 0.026) and cardioembolic stroke (OR: 1.02, 95% CI: 1.00–1.04, P = 0.028). There was no causal association of P‐wave terminal force in the precordial lead V1 (PTFVI), P-wave duration (PWD), NT-pro BNP or PR interval with ischemic stroke or any subtype.

scholarly journals Leukocyte telomere length and amyotrophic lateral sclerosis: a Mendelian randomization study

2021 ◽  
Author(s):  
Kailin Xia ◽  
Linjing Zhang ◽  
Gan Zhang ◽  
Yajun Wang ◽  
Tao Huang ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Telomere Length ◽  
Causal Relationship ◽  
Mendelian Randomization ◽  
Association Studies ◽  
Sensitivity Analyses ◽  
Genome Wide Association Studies ◽  
Leukocyte Telomere Length ◽  
Weighted Median ◽  
Lateral Sclerosis

Abstract Background Observational studies have suggested that telomere length is associated with amyotrophic lateral sclerosis (ALS). However, it remains unclear whether this association is causal. We employed a two-sample Mendelian randomization (MR) approach to explore the causal relationship between leukocyte telomere length (LTL) and ALS based on the most cited and most recent and largest LTL genome-wide association studies (GWASs) that measured LTL with the Southern blot method (n = 9190) and ALS GWAS summary data (n = 80,610). We adopted the inverse variance weighted (IVW) method to examine the effect of LTL on ALS and used the weighted median method, simple median method, MR Egger method and MR PRESSO method to perform sensitivity analyses. Results We found that genetically determined longer LTL was inversely associated with the risk of ALS (OR = 0.846, 95% CI: 0.744–0.962, P = 0.011), which was mainly driven by rs940209 in the OBFC1 gene, suggesting a potential effect of OBFC1 on ALS. In sensitivity analyses, that was confirmed in MR Egger method (OR = 0.647,95% CI = 0.447–0.936, P = 0.050), and a similar trend was shown with the weighted median method (OR = 0.893, P = 0.201) and simple median method (OR = 0.935 P = 0.535). The MR Egger analyses did not suggest directional pleiotropy, showing an intercept of 0.025 (P = 0.168). Neither the influence of instrumental outliers nor heterogeneity was found. Conclusions Our results suggest that genetically predicted longer LTL has a causal relationship with a lower risk of ALS and underscore the importance of protecting against telomere loss in ALS.

Circulating adiponectin levels and systemic lupus erythematosus: a two-sample Mendelian randomization study

Rheumatology ◽  
2020 ◽  
Author(s):  
Yi-Lin Dan ◽  
Peng Wang ◽  
Zhongle Cheng ◽  
Qian Wu ◽  
Xue-Rong Wang ◽  
...  
Keyword(s):  
Single Nucleotide Polymorphisms ◽  
Instrumental Variables ◽  
Mendelian Randomization ◽  
Causal Effect ◽  
Causal Effects ◽  
European Ancestry ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
Inverse Variance ◽  
Weighted Median

Abstract Objectives Several studies have reported increased serum/plasma adiponectin levels in SLE patients. This study was performed to estimate the causal effects of circulating adiponectin levels on SLE. Methods We selected nine independent single-nucleotide polymorphisms that were associated with circulating adiponectin levels (P < 5 × 10−8) as instrumental variables from a published genome-wide association study (GWAS) meta-analysis. The corresponding effects between instrumental variables and outcome (SLE) were obtained from an SLE GWAS analysis, including 7219 cases with 15 991 controls of European ancestry. Two-sample Mendelian randomization (MR) analyses with inverse-variance weighted, MR-Egger regression, weighted median and weight mode methods were used to evaluate the causal effects. Results The results of inverse-variance weighted methods showed no significantly causal associations of genetically predicted circulating adiponectin levels and the risk for SLE, with an odds ratio (OR) of 1.38 (95% CI 0.91, 1.35; P = 0.130). MR-Egger [OR 1.62 (95% CI 0.85, 1.54), P = 0.195], weighted median [OR 1.37 (95% CI 0.82, 1.35), P = 0.235) and weighted mode methods [OR 1.39 (95% CI 0.86, 1.38), P = 0.219] also supported no significant associations of circulating adiponectin levels and the risk for SLE. Furthermore, MR analyses in using SLE-associated single-nucleotide polymorphisms as an instrumental variable showed no associations of genetically predicted risk of SLE with circulating adiponectin levels. Conclusion Our study did not find evidence for a causal relationship between circulating adiponectin levels and the risk of SLE or of a causal effect of SLE on circulating adiponectin levels.

scholarly journals Causal Association Between mTOR-Dependent eIF4E mRNA Cap-Dependent Translation and Type 2 Diabetes: A Mendelian Randomization Study (OR31-02-19)

2019 ◽  
Vol 3 (Supplement_1) ◽  
Author(s):  
Ghada Soliman ◽  
C Mary Schooling
Keyword(s):  
Type 2 Diabetes ◽  
Sensitivity Analysis ◽  
Confidence Interval ◽  
Mendelian Randomization ◽  
Protein Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
P Value ◽  
Weighted Median

Abstract Objectives Type 2 diabetes is a prevalent chronic disease and is often associated with obesity and other comorbidities. The mammalian Target of Rapamycin complex 1 (mTORC1) nutrient-signaling pathway is a central regulator of cell growth and metabolism and is dysregulated in chronic diseases including diabetes and obesity. The eukaryotic translation initiation factor 4E (eIF-4E), a key regulator of gene translation and protein function, is under the control of mTOR and eIF4E Binding Proteins (4E-BPs). eIF-4E binds to the m7G (7-methylguanosine) cap at the 5’-UTR of most eukaryotic mRNA and mediates the recruitment of mRNA on ribosomes to start the protein translation. Both 4E-BP and ribosomal protein S6K kinase (S6K) are downstream effectors regulated by mTORC1 but converge to regulate two independent pathways. We investigated whether the risk of type 2 diabetes varied with genetically predicted eIF-4E and S6K levels using Mendelian Randomization (MR). Methods We estimated the causal role of eIF-4E and S6K plasma proteins, mTOR downstream targets, on type 2 diabetes, based on 16 single nucleotide polymorphisms (SNPs) for eIF-4E and 16 SNPs for S6K at P-value < 5x10−6. We applied these SNPs per exposure to publically available genetic associations with diabetes from the DIAbestes Genetics Replication And Meta-analysis (DIAGRAM) case (n = 26,676), and control (n = 132,532) study (mean age 57.4 years). We meta-analyzed SNP-specific Wald estimates using inverse variance weighting with multiplicative random effects. Sensitivity analysis was conducted using the weighted median, and MR-Egger estimates. Results eIF-4E cap-dependent translation factor was associated with lowered risk of type 2 diabetes with an odds ratio (OR) 0.94 per effect size, 95% confidence interval (0.88, 0.99, P = 0.03) with similar estimates from the weighted median and MR-Egger. S6K was not associated with diabetes, OR 0.95, 95% confidence interval (0.89, 1.01, P = 0.08). Sensitivity analysis using MR-Egger and weighed median analysis did not indicate pleiotropic effects suggesting a unique protective effect of eIF-4E on type 2 diabetes. Conclusions This unbiased Mendelian Randomization estimate is consistent with a causally protective association of eIF-4E on type 2 diabetes. eIF-4E may be a target for intervention by repurposing existing therapeutics to reduce the risk of type 2 diabetes. Funding Sources No specific funding.

scholarly journals Genetically increased serum calcium levels reduce Alzheimer’s disease risk

2018 ◽  
Author(s):  
Qinghua Jiang ◽  
Yang Hu ◽  
Shuilin Jin ◽  
Guiyou Liu
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Genetic Association ◽  
Serum Calcium ◽  
Genetic Variants ◽  
Large Scale ◽  
Mendelian Randomization ◽  
European Descent ◽  
Gwas Dataset ◽  
Weighted Median

AbstractIMPORTANCE Alzheimer’s disease (AD) is the leading cause of disability in the elderly. It has been a long time about the calcium hypothesis of AD on the basis of emerging evidence since 1994. However, most studies focused on the association between calcium homeostasis and AD, and concerned the intracellular calcium concentration. Only few studies reported reduced serum calcium levels in AD. Until now, it remains unclear whether serum calcium levels are genetically associated with AD risk.OBJECTIVE To evaluate the genetic association between increased serum calcium levels and AD riskDESIGN, SETTING, AND PARTICIPANTS We performed a Mendelian randomization study to investigate the association of increased serum calcium with AD risk using the genetic variants from the large-scale serum calcium genome-wide association study (GWAS) dataset (N=61,079 individuals of European descent) and the large-scale AD GWAS dataset (N=54,162 individuals including 17,008 AD cases and 37,154 controls of European descent). Inverse-variance weighted meta-analysis (IVW) was used to provide a combined estimate of the genetic association. Meanwhile, we selected the weighted median regression and MR-Egger regression as the complementary analysis methods to examine the robustness of the IVW estimate.EXPOSURES Genetic predisposition to increased serum calcium levelsMAIN OUTCOMES AND MEASURES The risk of AD.RESULTS We selected 6 independent genetic variants influencing serum calcium levels as the instrumental variables. IVW analysis showed that a genetically increased serum calcium level (per 1 standard deviation (SD) increase 0.5-mg/dL) was significantly associated with a reduced AD risk (OR=0.56, 95% CI: 0.34-0.94, P=5.00E-03). Meanwhile, both the weighted median estimate (OR=0.60, 95% CI: 0.34-1.06, P=0.08) and MR-Egger estimate (OR=0.66, 95% CI: 0.26-1.67, P=0.381) were consistent with the IVW estimate in terms of direction and magnitude.CONCLUSIONS AND RELEVANCE We provided evidence that genetically increased serum calcium levels could reduce the risk of AD. Meanwhile, randomized controlled study should be further conducted to assess the effect of serum calcium levels on AD risk, and further clarify whether diet calcium intake or calcium supplement, or both could reduce the risk of AD.Key PointsQuestion Is there a genetic relationship between elevated serum calcium levels and the risk of Alzheimer’s disease?Findings This Mendelian randomization study showed that the genetically increased serum calcium levels were associated with the reduced risk of Alzheimer’s disease.Meaning These findings provide evidence that genetically increased serum calcium levels could reduce the risk of Alzheimer’s disease.

scholarly journals Causal effects of serum levels of n-3 or n-6 polyunsaturated fatty acids on coronary artery disease: Mendelian randomization study

2020 ◽  
Author(s):  
Sehoon Park ◽  
Soojin Lee ◽  
Yaerim Kim ◽  
Yeonhee Lee ◽  
Min Woo Kang ◽  
...  
Keyword(s):  
Coronary Artery Disease ◽  
Fatty Acids ◽  
Linoleic Acid ◽  
Coronary Artery ◽  
Polyunsaturated Fatty Acids ◽  
Lower Risk ◽  
Mendelian Randomization ◽  
Causal Effects ◽  
Weighted Median ◽  
Artery Disease

AbstractBackgroundAdditional studies on the causal effects of 3-n and 6-n polyunsaturated fatty acids (PUFAs) on the risk of coronary artery disease (CAD) are warranted.MethodsThis Mendelian randomization (MR) study utilized a genetic instrument developed from previous genome-wide association studies for various serum 3-n and 6-n PUFA levels. First, we calculated the allele scores for genetic predisposition of PUFAs in individuals of European ancestry in the UK Biobank data (N=337,129). The allele score-based MR was obtained by regressing the allele scores to CAD risks. Second, summary-level MR was performed with the CARDIoGRAMplusC4D data for CAD (N=184,305). The inverse variance-weighted or Wald ratio method was the main analysis for the summary-level MR, and when multiple single nucleotide polymorphisms were utilized (e.g., linoleic acid), MR-Egger and weighted median methods were implemented as sensitivity analyses.ResultsHigher genetically predicted eicosapentaenoic acid and dihomo-gamma-linolenic acid levels were significantly associated with a lower risk of CAD both in the allele-score-based and summary-level MR analyses. Higher allele scores for linoleic acid level were significantly associated with lower CAD risks, and in the summary-level MR, the causal estimates by the MR-Egger and weighted median methods also indicated that higher linoleic acid levels cause a lower risk of CAD. Arachidonic acid was the 6-n PUFA that showed significant causal estimates for a higher risk of CAD. Higher docosapentaenoic acid and adrenic acid levels showed inconsistent findings in the MR analysis results.ConclusionsThis study supports the causal effects of certain 3-n and 6-n PUFA types on the risk of CAD.

scholarly journals Causal relationships between genetically determined metabolites and human intelligence: A Mendelian randomization study

2020 ◽  
Author(s):  
Jian Yang ◽  
Binbin Zhao ◽  
Li Qian ◽  
Fengjie Gao ◽  
Yanjuan Fan ◽  
...  
Keyword(s):  
Complex Traits ◽  
Mendelian Randomization ◽  
Sensitivity Analyses ◽  
Human Intelligence ◽  
Causal Relationships ◽  
Biological Mechanisms ◽  
Inverse Variance ◽  
Weighted Median ◽  
Genetic And Environmental Factors ◽  
Genetically Determined

Abstract Intelligence predicts important life and health outcomes, but the biological mechanisms underlying differences in intelligence are not yet understood. The use of genetically determined metabotypes (GDMs) to understand the role of genetic and environmental factors, and their interactions, in human complex traits has been recently proposed. However, this strategy has not been applied to human intelligence. Here we implemented a two-sample Mendelian randomization (MR) analysis using GDMs to assess the causal relationships between genetically determined metabolites and human intelligence. The standard inverse-variance weighted (IVW) method was used for the primary MR analysis and three additional MR methods (MR-Egger, weighted median, and MR-PRESSO) were used for sensitivity analyses. Using 25 genetic variants as instrumental variables (IVs), our study found that 5-oxoproline was associated with better performance in human intelligence tests (P IVW = 9 · 25×10 -5 ). The causal relationship was robust when sensitivity analyses were applied (P MR-Egger = 0 · 0001, P Weighted median = 6 · 29×10 -6 , P MR-PRESSO = 0 · 0007), and no evidence of horizontal pleiotropy was observed. Similarly, also dihomo-linoleate (20:2n6) and p-acetamidophenylglucuronide showed robust association with intelligence. Our study provides novel insight by integrating genomics and metabolomics to estimate causal effects of genetically determined metabolites on human intelligence, which help to understanding of the biological mechanisms related to human intelligence.

Causal association of adipokines with osteoarthritis: a Mendelian randomization study

Rheumatology ◽  
2020 ◽  
Author(s):  
Jiayao Fan ◽  
Jiahao Zhu ◽  
Lingling Sun ◽  
Yasong Li ◽  
Tianle Wang ◽  
...  
Keyword(s):  
Mendelian Randomization ◽  
Association Studies ◽  
Genome Wide Association ◽  
Sensitivity Analyses ◽  
European Ancestry ◽  
Genome Wide Association Studies ◽  
Knee Oa ◽  
Genome Wide ◽  
A Genome ◽  
Weighted Median

Abstract Objective This two-sample Mendelian randomization study aimed to delve into the effects of genetically predicted adipokine levels on OA. Methods Summary statistic data for OA originated from a meta-analysis of a genome-wide association study with an overall 50 508 subjects of European ancestry. Publicly available summary data from four genome-wide association studies were exploited to respectively identify instrumental variables of adiponectin, leptin, resistin, chemerin and retinol-blinding protein 4. Subsequently, Mendelian randomization analyses were conducted with inverse variance weighted (IVW), weighted median and Mendelian randomization-Egger regression. Furthermore, sensitivity analyses were then conducted to assess the robustness of our results. Results The positive causality between genetically predicted leptin level and risk of total OA was indicated by IVW [odds ratio (OR): 2.40, 95% CI: 1.13–5.09] and weighted median (OR: 2.94, 95% CI: 1.23–6.99). In subgroup analyses, evidence of potential harmful effects of higher level of adiponectin (OR: 1.28, 95% CI: 1.01–1.61 using IVW), leptin (OR: 3.44, 95% CI: 1.18–10.03 using IVW) and resistin (OR: 1.18, 95% CI: 1.03–1.36 using IVW) on risk of knee OA were acquired. However, the mentioned effects on risk of hip OA were not statistically significant. Slight evidence was identified supporting causality of chemerin and retinol-blinding protein 4 for OA. The findings of this study were verified by the results from sensitivity analysis. Conclusions An association between genetically predicted leptin level and risk of total OA was identified. Furthermore, association of genetically predicted levels of adiponectin, leptin and resistin with risk of knee OA were reported.

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