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Testing for non-linear causal effects using a binary genotype in a Mendelian randomization study: application to alcohol and cardiovascular traits.
Int J Epidemiol
PUBLISHED: 09-05-2014
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Mendelian randomization studies have so far restricted attention to linear associations relating the genetic instrument to the exposure, and the exposure to the outcome. In some cases, however, observational data suggest a non-linear association between exposure and outcome. For example, alcohol consumption is consistently reported as having a U-shaped association with cardiovascular events. In principle, Mendelian randomization could address concerns that the apparent protective effect of light-to-moderate drinking might reflect 'sick-quitters' and confounding.
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Systematic review and metaanalysis of genetic association studies of urinary symptoms and prolapse in women.
Am. J. Obstet. Gynecol.
PUBLISHED: 08-08-2014
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Family studies and twin studies demonstrate that lower urinary tract symptoms and pelvic organ prolapse are heritable. This review aimed to identify genetic polymorphisms tested for an association with lower urinary tract symptoms or prolapse, and to assess the strength, consistency, and risk of bias among reported associations.
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Association between alcohol and cardiovascular disease: Mendelian randomisation analysis based on individual participant data.
Michael V Holmes, Caroline E Dale, Luisa Zuccolo, Richard J Silverwood, Yiran Guo, Zheng Ye, David Prieto-Merino, Abbas Dehghan, Stella Trompet, Andrew Wong, Alana Cavadino, Dagmar Drogan, Sandosh Padmanabhan, Shanshan Li, Ajay Yesupriya, Maarten Leusink, Johan Sundström, Jaroslav A Hubacek, Hynek Pikhart, Daniel I Swerdlow, Andrie G Panayiotou, Svetlana A Borinskaya, Chris Finan, Sonia Shah, Karoline B Kuchenbaecker, Tina Shah, Jorgen Engmann, Lasse Folkersen, Per Eriksson, Fulvio Ricceri, Olle Melander, Carlotta Sacerdote, Dale M Gamble, Sruti Rayaprolu, Owen A Ross, Stela McLachlan, Olga Vikhireva, Ivonne Sluijs, Robert A Scott, Vera Adamkova, Leon Flicker, Frank M van Bockxmeer, Christine Power, Pedro Marques-Vidal, Tom Meade, Michael G Marmot, José M Ferro, Sofia Paulos-Pinheiro, Steve E Humphries, Philippa J Talmud, Irene Mateo Leach, Niek Verweij, Allan Linneberg, Tea Skaaby, Pieter A Doevendans, Maarten J Cramer, Pim van der Harst, Olaf H Klungel, Nicole F Dowling, Anna F Dominiczak, Meena Kumari, Andrew N Nicolaides, Cornelia Weikert, Heiner Boeing, Shah Ebrahim, Tom R Gaunt, Jackie F Price, Lars Lannfelt, Anne Peasey, Růžena Kubinova, Andrzej Pająk, Sofia Malyutina, Mikhail I Voevoda, Abdonas Tamosiunas, Anke H Maitland-van der Zee, Paul E Norman, Graeme J Hankey, Manuela M Bergmann, Albert Hofman, Oscar H Franco, Jackie Cooper, Jutta Palmen, Wilko Spiering, Pim A de Jong, Diana Kuh, Rebecca Hardy, André G Uitterlinden, M Arfan Ikram, Ian Ford, Elina Hyppönen, Osvaldo P Almeida, Nicholas J Wareham, Kay-Tee Khaw, Anders Hamsten, Lise Lotte N Husemoen, Anne Tjønneland, Janne S Tolstrup, Eric Rimm, Joline W J Beulens, W M Monique Verschuren, N Charlotte Onland-Moret, Marten H Hofker, S Goya Wannamethee, Peter H Whincup, Richard Morris, Astrid M Vicente, Hugh Watkins, Martin Farrall, J Wouter Jukema, James Meschia, L Adrienne Cupples, Stephen J Sharp, Myriam Fornage, Charles Kooperberg, Andrea Z LaCroix, James Y Dai, Matthew B Lanktree, David S Siscovick, Eric Jorgenson, Bonnie Spring, Josef Coresh, Yun R Li, Sarah G Buxbaum, Pamela J Schreiner, R Curtis Ellison, Michael Y Tsai, Sanjay R Patel, Susan Redline, Andrew D Johnson, Ron C Hoogeveen, Hakon Hakonarson, Jerome I Rotter, Eric Boerwinkle, Paul I W de Bakker, Mika Kivimäki, Folkert W Asselbergs, Naveed Sattar, Debbie A Lawlor, John Whittaker, George Davey Smith, Kenneth Mukamal, Bruce M Psaty, James G Wilson, Leslie A Lange, Ajna Hamidovic, Aroon D Hingorani, Børge G Nordestgaard, Martin Bobak, David A Leon, Claudia Langenberg, Tom M Palmer, Alex P Reiner, Brendan J Keating, Frank Dudbridge, Juan P Casas, .
BMJ
PUBLISHED: 07-12-2014
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To use the rs1229984 variant in the alcohol dehydrogenase 1B gene (ADH1B) as an instrument to investigate the causal role of alcohol in cardiovascular disease.
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Effects of BMI, fat mass, and lean mass on asthma in childhood: a Mendelian randomization study.
PLoS Med.
PUBLISHED: 07-01-2014
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Observational studies have reported associations between body mass index (BMI) and asthma, but confounding and reverse causality remain plausible explanations. We aim to investigate evidence for a causal effect of BMI on asthma using a Mendelian randomization approach.
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Lack of identification in semiparametric instrumental variable models with binary outcomes.
Am. J. Epidemiol.
PUBLISHED: 05-23-2014
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A parameter in a statistical model is identified if its value can be uniquely determined from the distribution of the observable data. We consider the context of an instrumental variable analysis with a binary outcome for estimating a causal risk ratio. The semiparametric generalized method of moments and structural mean model frameworks use estimating equations for parameter estimation. In this paper, we demonstrate that lack of identification can occur in either of these frameworks, especially if the instrument is weak. In particular, the estimating equations may have no solution or multiple solutions. We investigate the relationship between the strength of the instrument and the proportion of simulated data sets for which there is a unique solution of the estimating equations. We see that this proportion does not appear to depend greatly on the sample size, particularly for weak instruments (?(2) ? 0.01). Poor identification was observed in a considerable proportion of simulated data sets for instruments explaining up to 10% of the variance in the exposure with sample sizes up to 1 million. In an applied example considering the causal effect of body mass index (weight (kg)/height (m)(2)) on the probability of early menarche, estimates and standard errors from an automated optimization routine were misleading.
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Mendelian randomization of blood lipids for coronary heart disease.
Eur. Heart J.
PUBLISHED: 01-30-2014
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To investigate the causal role of high-density lipoprotein cholesterol (HDL-C) and triglycerides in coronary heart disease (CHD) using multiple instrumental variables for Mendelian randomization.
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Causal effects of body mass index on cardiometabolic traits and events: a Mendelian randomization analysis.
Am. J. Hum. Genet.
PUBLISHED: 01-23-2014
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Elevated body mass index (BMI) associates with cardiometabolic traits on observational analysis, yet the underlying causal relationships remain unclear. We conducted Mendelian randomization analyses by using a genetic score (GS) comprising 14 BMI-associated SNPs from a recent discovery analysis to investigate the causal role of BMI in cardiometabolic traits and events. We used eight population-based cohorts, including 34,538 European-descent individuals (4,407 type 2 diabetes (T2D), 6,073 coronary heart disease (CHD), and 3,813 stroke cases). A 1 kg/m(2) genetically elevated BMI increased fasting glucose (0.18 mmol/l; 95% confidence interval (CI) = 0.12-0.24), fasting insulin (8.5%; 95% CI = 5.9-11.1), interleukin-6 (7.0%; 95% CI = 4.0-10.1), and systolic blood pressure (0.70 mmHg; 95% CI = 0.24-1.16) and reduced high-density lipoprotein cholesterol (-0.02 mmol/l; 95% CI = -0.03 to -0.01) and low-density lipoprotein cholesterol (LDL-C; -0.04 mmol/l; 95% CI = -0.07 to -0.01). Observational and causal estimates were directionally concordant, except for LDL-C. A 1 kg/m(2) genetically elevated BMI increased the odds of T2D (odds ratio [OR] = 1.27; 95% CI = 1.18-1.36) but did not alter risk of CHD (OR 1.01; 95% CI = 0.94-1.08) or stroke (OR = 1.03; 95% CI = 0.95-1.12). A meta-analysis incorporating published studies reporting 27,465 CHD events in 219,423 individuals yielded a pooled OR of 1.04 (95% CI = 0.97-1.12) per 1 kg/m(2) increase in BMI. In conclusion, we identified causal effects of BMI on several cardiometabolic traits; however, whether BMI causally impacts CHD risk requires further evidence.
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Systematic review and meta-analysis of candidate gene association studies of lower urinary tract symptoms in men.
Eur. Urol.
PUBLISHED: 01-10-2014
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Although family studies have shown that male lower urinary tract symptoms (LUTS) are highly heritable, no systematic review exists of genetic polymorphisms tested for association with LUTS.
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Genetic variants at chromosome 9p21 and risk of first versus subsequent coronary heart disease events: a systematic review and meta-analysis.
J. Am. Coll. Cardiol.
PUBLISHED: 01-07-2014
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The purpose of this analysis was to compare the association between variants at the chromosome 9p21 locus (Ch9p21) and risk of first versus subsequent coronary heart disease (CHD) events through systematic review and meta-analysis.
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Effects of Promoting Longer Term and Exclusive Breastfeeding on Cardiometabolic Risk Factors at Age 11.5 Years: A Cluster-Randomized, Controlled Trial.
Circulation
PUBLISHED: 12-03-2013
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The duration and exclusivity of breastfeeding in infancy have been inversely associated with future cardiometabolic risk. We investigated the effects of an experimental intervention to promote increased duration of exclusive breastfeeding on cardiometabolic risk factors in childhood.
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Association of plasma uric acid with ischaemic heart disease and blood pressure: mendelian randomisation analysis of two large cohorts.
BMJ
PUBLISHED: 07-23-2013
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To assess the associations between both uric acid levels and hyperuricaemia, with ischaemic heart disease and blood pressure, and to explore the potentially confounding role of body mass index.
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Secretory Phospholipase A2-IIA and Cardiovascular Disease: A Mendelian Randomization Study.
Michael V Holmes, Tabassome Simon, Holly J Exeter, Lasse Folkersen, Folkert W Asselbergs, Montse Guardiola, Jackie A Cooper, Jutta Palmen, Jaroslav A Hubacek, Kathryn F Carruthers, Benjamin D Horne, Kimberly D Brunisholz, Jessica L Mega, Erik P A van Iperen, Mingyao Li, Maarten Leusink, Stella Trompet, Jeffrey J W Verschuren, G Kees Hovingh, Abbas Dehghan, Christopher P Nelson, Salma Kotti, Nicolas Danchin, Markus Scholz, Christiane L Haase, Dietrich Rothenbacher, Daniel I Swerdlow, Karoline B Kuchenbaecker, Eleonora Staines-Urias, Anuj Goel, Ferdinand van 't Hooft, Karl Gertow, Ulf de Faire, Andrie G Panayiotou, Elena Tremoli, Damiano Baldassarre, Fabrizio Veglia, Lesca M Holdt, Frank Beutner, Ron T Gansevoort, Gerjan J Navis, Irene Mateo Leach, Lutz P Breitling, Hermann Brenner, Joachim Thiery, Dhayana Dallmeier, Anders Franco-Cereceda, Jolanda M A Boer, Jeffrey W Stephens, Marten H Hofker, Alain Tedgui, Albert Hofman, André G Uitterlinden, Vera Adamkova, Jan Piťha, N Charlotte Onland-Moret, Maarten J Cramer, Hendrik M Nathoe, Wilko Spiering, Olaf H Klungel, Meena Kumari, Peter H Whincup, David A Morrow, Peter S Braund, Alistair S Hall, Anders G Olsson, Pieter A Doevendans, Mieke D Trip, Martin D Tobin, Anders Hamsten, Hugh Watkins, Wolfgang Koenig, Andrew N Nicolaides, Daniel Teupser, Ian N M Day, John F Carlquist, Tom R Gaunt, Ian Ford, Naveed Sattar, Sotirios Tsimikas, Gregory G Schwartz, Debbie A Lawlor, Richard W Morris, Manjinder S Sandhu, Rudolf Poledne, Anke H Maitland-van der Zee, Kay-Tee Khaw, Brendan J Keating, Pim van der Harst, Jackie F Price, Shamir R Mehta, Salim Yusuf, Jaqueline C M Witteman, Oscar H Franco, J Wouter Jukema, Peter de Knijff, Anne Tybjaerg-Hansen, Daniel J Rader, Martin Farrall, Nilesh J Samani, Mika Kivimäki, Keith A A Fox, Steve E Humphries, Jeffrey L Anderson, S Matthijs Boekholdt, Tom M Palmer, Per Eriksson, Guillaume Paré, Aroon D Hingorani, Marc S Sabatine, Ziad Mallat, Juan P Casas, Philippa J Talmud.
J. Am. Coll. Cardiol.
PUBLISHED: 04-24-2013
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This study sought to investigate the role of secretory phospholipase A2 (sPLA2)-IIA in cardiovascular disease.
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The causal roles of vitamin B(12) and transcobalamin in prostate cancer: can Mendelian randomization analysis provide definitive answers?
Int J Mol Epidemiol Genet
PUBLISHED: 07-23-2011
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Circulating vitamin B(12) (cobalamin/B(12)) and total transcobalamin (tTC) have been associated with increased and reduced risk, respectively, of prostate cancer. Mendelian randomization has the potential to determine whether these are causal associations. We estimated associations of single nucleotide polymorphisms in B(12)-related genes (MTR, MTRR, FUT2, TCN2, TCN1, CUBN, and MUT) with plasma concentrations of B(12), tTC, holo-transcobalamin, holo-haptocorrin, folate, and homocysteine and with prostate cancer risk in a case-control study (913 cases, 895 controls) nested within the UK-wide population-based ProtecT study of prostate cancer in men age 45-69 years. Instrumental variable (IV) analysis was used to estimate odds ratios for effects of B(12) and tTC on prostate cancer. We observed that B(12) was lower in men with FUT2 204G>A (rs492602), CUBN 758C>T (rs1801222) and MUT 1595G>A (rs1141321) alleles (P(trend)<0.001); tTC was lower in men with the TCN2 776C>G (rs1801198) allele (P(trend)<0.001). FUT2 204G>A and CUBN 758C>T were selected as instruments for B(12); TCN2 776C>G for tTC. Conventional and IV estimates for the association of log(e)(B(12)) with prostate cancer were: OR=1.17 (95% CI 0.90-1.51), P=0.2 and OR=0.60 (0.16-2.15), P=0.4, respectively. Conventional and IV estimates for the association of loge(tTC) with prostate cancer were: OR=0.81 (0.54-1.20), P=0.3 and OR=0.41 (0.13-1.32), P=0.1, respectively. Confidence intervals around the IV estimates in our study were too wide to allow robust inference. Sample size estimates based on our data indicated that Mendelian randomization in this context requires much larger studies or multiple genetic variants that explain all of the variance in the intermediate phenotype.
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Smoking is associated with, but does not cause, depressed mood in pregnancy--a mendelian randomization study.
PLoS ONE
PUBLISHED: 06-08-2011
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Smokers have a higher prevalence of major depressive episodes and depressive symptoms than the general population, but whether this association is causal, or is due to confounding or reverse causation is uncertain because of the problems inherent in some epidemiological studies. Mendelian randomization, in which a genetic variant is used as a surrogate for measuring exposure, is an approach which may be used to better understand this association. We investigated the rs1051730 single nucleotide polymorphism in the nicotine acetylcholine receptor gene cluster (CHRNA5-CHRNA3-CHRNB4), associated with smoking phenotypes, to determine whether women who continued to smoke were also more likely to report a low mood during pregnancy. We found among women who smoked pre-pregnancy, those with the 1051730 T allele smoked more and were less likely to quit smoking during pregnancy, but were also less likely to report high levels of depressed mood at 18 weeks of pregnancy (per allele OR?=?0.84, 95%CI 0.72 to 0.99, p?=?0.034). The association between genotype and depressed mood was limited to women who were smokers prior to pregnancy, with weak evidence of an interaction between smoking status and genotype (p?=?0.07). Our results do not support a causal role of smoking on depressed mood, but are consistent with a self-medication hypothesis, whereby smoking is used to alleviate symptoms of depression. A replication study using multiple genetic variants which influence smoking via different pathways is required to confirm these findings and provide evidence that the genetic variant is reflecting the effect of quitting smoking on depressed mood, and is not directly affecting mood.
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Maternal and offspring adiposity-related genetic variants and gestational weight gain.
Am. J. Clin. Nutr.
PUBLISHED: 05-18-2011
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Gestational weight gain (GWG) is associated with a range of health outcomes, but little is known about the factors that influence it.
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Instrumental variable estimation of causal risk ratios and causal odds ratios in Mendelian randomization analyses.
Am. J. Epidemiol.
PUBLISHED: 05-09-2011
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In this paper, the authors describe different instrumental variable (IV) estimators of causal risk ratios and odds ratios with particular attention to methods that can handle continuously measured exposures. The authors present this discussion in the context of a Mendelian randomization analysis of the effect of body mass index (BMI; weight (kg)/height (m)(2)) on the risk of asthma at age 7 years (Avon Longitudinal Study of Parents and Children, 1991-1992). The authors show that the multiplicative structural mean model (MSMM) and the multiplicative generalized method of moments (MGMM) estimator produce identical estimates of the causal risk ratio. In the example, MSMM and MGMM estimates suggested an inverse relation between BMI and asthma but other IV estimates suggested a positive relation, although all estimates had wide confidence intervals. An interaction between the associations of BMI and fat mass and obesity-associated (FTO) genotype with asthma explained the different directions of the different estimates, and a simulation study supported the observation that MSMM/MGMM estimators are negatively correlated with the other estimators when such an interaction is present. The authors conclude that point estimates from various IV methods can differ in practical applications. Based on the theoretical properties of the estimators, structural mean models make weaker assumptions than other IV estimators and can therefore be expected to be consistent in a wider range of situations.
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Mendelian randomization studies do not support a role for raised circulating triglyceride levels influencing type 2 diabetes, glucose levels, or insulin resistance.
Diabetes
PUBLISHED: 01-31-2011
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The causal nature of associations between circulating triglycerides, insulin resistance, and type 2 diabetes is unclear. We aimed to use Mendelian randomization to test the hypothesis that raised circulating triglyceride levels causally influence the risk of type 2 diabetes and raise normal fasting glucose levels and hepatic insulin resistance.
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Using multiple genetic variants as instrumental variables for modifiable risk factors.
Stat Methods Med Res
PUBLISHED: 01-07-2011
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Mendelian randomisation analyses use genetic variants as instrumental variables (IVs) to estimate causal effects of modifiable risk factors on disease outcomes. Genetic variants typically explain a small proportion of the variability in risk factors; hence Mendelian randomisation analyses can require large sample sizes. However, an increasing number of genetic variants have been found to be robustly associated with disease-related outcomes in genome-wide association studies. Use of multiple instruments can improve the precision of IV estimates, and also permit examination of underlying IV assumptions. We discuss the use of multiple genetic variants in Mendelian randomisation analyses with continuous outcome variables where all relationships are assumed to be linear. We describe possible violations of IV assumptions, and how multiple instrument analyses can be used to identify them. We present an example using four adiposity-associated genetic variants as IVs for the causal effect of fat mass on bone density, using data on 5509 children enrolled in the ALSPAC birth cohort study. We also use simulation studies to examine the effect of different sets of IVs on precision and bias. When each instrument independently explains variability in the risk factor, use of multiple instruments increases the precision of IV estimates. However, inclusion of weak instruments could increase finite sample bias. Missing data on multiple genetic variants can diminish the available sample size, compared with single instrument analyses. In simulations with additive genotype-risk factor effects, IV estimates using a weighted allele score had similar properties to estimates using multiple instruments. Under the correct conditions, multiple instrument analyses are a promising approach for Mendelian randomisation studies. Further research is required into multiple imputation methods to address missing data issues in IV estimation.
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Associations between an obesity related genetic variant (FTO rs9939609) and prostate cancer risk.
PLoS ONE
PUBLISHED: 06-24-2010
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Observational studies suggest that obese men have a lower risk of incident prostate cancer, but an increased risk of advanced and fatal cancers. These observations could be due to confounding, detection bias, or a biological effect of obesity. Genetic studies are less susceptible to confounding than observational epidemiology and can suggest how associations between phenotypes (such as obesity) and diseases arise. To determine whether the associations between obesity and prostate cancer are causal, we conducted a genetic association study of the relationship between a single nucleotide polymorphism known to be associated with obesity (FTO rs9939609) and prostate cancer. Data are from a population-based sample of 1550 screen-detected prostate cancers, 1815 age- and general practice matched controls with unrestricted prostate specific antigen (PSA) values and 1175 low-PSA controls (PSA <0.5 ng/ml). The rs9939609 A allele, which was associated with higher BMI in the sample, was inversely associated with overall (odds ratio (OR) versus all controls ?= 0.93; 95% confidence interval (CI): 0.85-1.02 p = 0.12 per allele) and low-grade (OR = 0.90; 0.81-0.99 p = 0.03 per allele) prostate cancer risk, but positively associated with high-grade cancer among cases (OR high- versus low-grade cancer ?= 1.16; 0.99-1.37 p = 0.07 per allele). Although evidence for these effects was weak, they are consistent with observational data based on BMI phenotypes and suggest that the observed association between obesity and prostate cancer is not due to confounding. Further research should confirm these findings, extend them to other BMI-related genetic variants and determine whether they are due to detection bias or obesity-related hormonal changes.
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Novel methods to deal with publication biases: secondary analysis of antidepressant trials in the FDA trial registry database and related journal publications.
BMJ
PUBLISHED: 08-12-2009
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To assess the performance of novel contour enhanced funnel plots and a regression based adjustment method to detect and adjust for publication biases.
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Severity of bias of a simple estimator of the causal odds ratio in Mendelian randomization studies.
Stat Med
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Mendelian randomization studies estimate causal effects using genetic variants as instruments. Instrumental variable methods are straightforward for linear models, but epidemiologists often use odds ratios to quantify effects. Also, odds ratios are often the quantities reported in meta-analyses. Many applications of Mendelian randomization dichotomize genotype and estimate the population causal log odds ratio for unit increase in exposure by dividing the genotype-disease log odds ratio by the difference in mean exposure between genotypes. This Wald-type estimator is biased even in large samples, but whether the magnitude of bias is of practical importance is unclear. We study the large-sample bias of this estimator in a simple model with a continuous normally distributed exposure, a single unobserved confounder that is not an effect modifier, and interpretable parameters. We focus on parameter values that reflect scenarios in which we apply Mendelian randomization, including realistic values for the degree of confounding and strength of the causal effect. We evaluate this estimator and the causal odds ratio using numerical integration and obtain approximate analytic expressions to check results and gain insight. A small simulation study examines finite sample bias and mild violations of the normality assumption. For our simple data-generating model, we find that the Wald estimator is asymptotically biased with a bias of around 10% in fairly typical Mendelian randomization scenarios but which can be larger in more extreme situations. Recently developed methods such as structural mean models require fewer untestable assumptions and we recommend their use when the individual-level data they require are available. The Wald-type estimator may retain a role as an approximate method for meta-analysis based on summary data.
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Multivariate multilevel spline models for parallel growth processes: application to weight and mean arterial pressure in pregnancy.
Stat Med
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Growth models are commonly used in life course epidemiology to describe growth trajectories and their determinants or to relate particular patterns of change to later health outcomes. However, methods to analyse relationships between two or more change processes occurring in parallel, in particular to assess evidence for causal influences of change in one variable on subsequent changes in another, are less developed. We discuss linear spline multilevel models with a multivariate response and show how these can be used to relate rates of change in a particular time period in one variable to later rates of change in another variable by using the variances and covariances of individual-level random effects for each of the splines. We describe how regression coefficients can be calculated for these associations and how these can be adjusted for other parameters such as random effect variables relating to baseline values or rates of change in earlier time periods, and compare different methods for calculating the standard errors of these regression coefficients. We also show that these models can equivalently be fitted in the structural equation modelling framework and apply each method to weight and mean arterial pressure changes during pregnancy, obtaining similar results for multilevel and structural equation models. This method improves on the multivariate linear growth models, which have been used previously to model parallel processes because it enables nonlinear patterns of change to be modelled and the temporal sequence of multivariate changes to be determined, with adjustment for change in earlier time periods.
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Instrumental variable estimation of the causal effect of plasma 25-hydroxy-vitamin D on colorectal cancer risk: a mendelian randomization analysis.
PLoS ONE
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Vitamin D deficiency has been associated with several common diseases, including cancer and is being investigated as a possible risk factor for these conditions. We reported the striking prevalence of vitamin D deficiency in Scotland. Previous epidemiological studies have reported an association between low dietary vitamin D and colorectal cancer (CRC). Using a case-control study design, we tested the association between plasma 25-hydroxy-vitamin D (25-OHD) and CRC (2,001 cases, 2,237 controls). To determine whether plasma 25-OHD levels are causally linked to CRC risk, we applied the control function instrumental variable (IV) method of the mendelian randomization (MR) approach using four single nucleotide polymorphisms (rs2282679, rs12785878, rs10741657, rs6013897) previously shown to be associated with plasma 25-OHD. Low plasma 25-OHD levels were associated with CRC risk in the crude model (odds ratio (OR): 0.76, 95% Confidence Interval (CI): 0.71, 0.81, p: 1.4×10(-14)) and after adjusting for age, sex and other confounding factors. Using an allele score that combined all four SNPs as the IV, the estimated causal effect was OR 1.16 (95% CI 0.60, 2.23), whilst it was 0.94 (95% CI 0.46, 1.91) and 0.93 (0.53, 1.63) when using an upstream (rs12785878, rs10741657) and a downstream allele score (rs2282679, rs6013897), respectively. 25-OHD levels were inversely associated with CRC risk, in agreement with recent meta-analyses. The fact that this finding was not replicated when the MR approach was employed might be due to weak instruments, giving low power to demonstrate an effect (<0.35). The prevalence and degree of vitamin D deficiency amongst individuals living in northerly latitudes is of considerable importance because of its relationship to disease. To elucidate the effect of vitamin D on CRC cancer risk, additional large studies of vitamin D and CRC risk are required and/or the application of alternative methods that are less sensitive to weak instrument restrictions.
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The effect of elevated body mass index on ischemic heart disease risk: causal estimates from a Mendelian randomisation approach.
PLoS Med.
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Adiposity, assessed as elevated body mass index (BMI), is associated with increased risk of ischemic heart disease (IHD); however, whether this is causal is unknown. We tested the hypothesis that positive observational associations between BMI and IHD are causal.
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Associations of mortality with own height using sons height as an instrumental variable.
Econ Hum Biol
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Height is associated with mortality from many diseases, but it remains unclear whether the association is causal or due to confounding by social factors, genetic pleiotropy,(1) or existing ill-health. The authors investigated whether the association of height with mortality is causal by using a sons height as an instrumental variable (IV) for parents height among the parents of a cohort of 1,036,963 Swedish men born between 1951 and 1980 who had their height measured at military conscription, aged around 18, between 1969 and 2001. In a two-sample IV analysis adjusting for sons age at examination and secular trends in height, as well as parental age, and socioeconomic position, the hazard ratio (HR) for all-cause paternal mortality per standard deviation (SD, 6.49cm) of height was 0.96 (95% confidence interval (CI): 0.95, 0.96). The results of IV analyses of mortality from all causes, cardiovascular disease (CVD), respiratory disease, cancer, external causes and suicide were comparable to those obtained using sons height as a simple proxy for own height and to conventional analyses of own height in the present data and elsewhere, suggesting that such conventional analyses are not substantially confounded by existing ill-health.
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Association between genetic variants on chromosome 15q25 locus and objective measures of tobacco exposure.
J. Natl. Cancer Inst.
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Two single-nucleotide polymorphisms, rs1051730 and rs16969968, located within the nicotinic acetylcholine receptor gene cluster on chromosome 15q25 locus, are associated with heaviness of smoking, risk for lung cancer, and other smoking-related health outcomes. Previous studies have typically relied on self-reported smoking behavior, which may not fully capture interindividual variation in tobacco exposure.
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What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

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We use abstracts found on PubMed and match them to JoVE videos to create a list of 10 to 30 related methods videos.

Video X seems to be unrelated to Abstract Y...

In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.