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Power GM, Sanderson E, Pagoni P, Fraser A, Morris T, Prince C, Frayling TM, Heron J, Richardson TG, Richmond R, Tyrrell J, Warrington N, Davey Smith G, Howe LD, Tilling KM. Methodological approaches, challenges, and opportunities in the application of Mendelian randomisation to lifecourse epidemiology: A systematic literature review. Eur J Epidemiol 2024; 39:501-520. [PMID: 37938447 PMCID: PMC7616129 DOI: 10.1007/s10654-023-01032-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 07/21/2023] [Indexed: 11/09/2023]
Abstract
Diseases diagnosed in adulthood may have antecedents throughout (including prenatal) life. Gaining a better understanding of how exposures at different stages in the lifecourse influence health outcomes is key to elucidating the potential benefits of disease prevention strategies. Mendelian randomisation (MR) is increasingly used to estimate causal effects of exposures across the lifecourse on later life outcomes. This systematic literature review explores MR methods used to perform lifecourse investigations and reviews previous work that has utilised MR to elucidate the effects of factors acting at different stages of the lifecourse. We conducted searches in PubMed, Embase, Medline and MedRXiv databases. Thirteen methodological studies were identified. Four studies focused on the impact of time-varying exposures in the interpretation of "standard" MR techniques, five presented methods for repeat measures of the same exposure, and four described methodological approaches to handling multigenerational exposures. A further 127 studies presented the results of an applied research question. Over half of these estimated effects in a single generation and were largely confined to the exploration of questions regarding body composition. The remaining mostly estimated maternal effects. There is a growing body of research focused on the development and application of MR methods to address lifecourse research questions. The underlying assumptions require careful consideration and the interpretation of results rely on select conditions. Whilst we do not advocate for a particular strategy, we encourage practitioners to make informed decisions on how to approach a research question in this field with a solid understanding of the limitations present and how these may be affected by the research question, modelling approach, instrument selection, and data availability.
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Affiliation(s)
- Grace M Power
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK.
- Population Health Sciences, Bristol Medical School, University of Bristol, Oakfield House, Oakfield Grove, Bristol, BS8 2BN, UK.
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia.
| | - Eleanor Sanderson
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
- Population Health Sciences, Bristol Medical School, University of Bristol, Oakfield House, Oakfield Grove, Bristol, BS8 2BN, UK
| | - Panagiota Pagoni
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
- Population Health Sciences, Bristol Medical School, University of Bristol, Oakfield House, Oakfield Grove, Bristol, BS8 2BN, UK
| | - Abigail Fraser
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
- Population Health Sciences, Bristol Medical School, University of Bristol, Oakfield House, Oakfield Grove, Bristol, BS8 2BN, UK
| | - Tim Morris
- Centre for Longitudinal Studies, Social Research Institute, University College London, London, UK
| | - Claire Prince
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
- Population Health Sciences, Bristol Medical School, University of Bristol, Oakfield House, Oakfield Grove, Bristol, BS8 2BN, UK
| | - Timothy M Frayling
- Genetics of Complex Traits, College of Medicine and Health, University of Exeter, Exeter, UK
| | - Jon Heron
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
- Population Health Sciences, Bristol Medical School, University of Bristol, Oakfield House, Oakfield Grove, Bristol, BS8 2BN, UK
| | - Tom G Richardson
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
- Population Health Sciences, Bristol Medical School, University of Bristol, Oakfield House, Oakfield Grove, Bristol, BS8 2BN, UK
| | - Rebecca Richmond
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
- Population Health Sciences, Bristol Medical School, University of Bristol, Oakfield House, Oakfield Grove, Bristol, BS8 2BN, UK
| | - Jessica Tyrrell
- Genetics of Complex Traits, College of Medicine and Health, University of Exeter, Exeter, UK
| | - Nicole Warrington
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
- Frazer Institute, University of Queensland, Woolloongabba, Queensland, Australia
| | - George Davey Smith
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
- Population Health Sciences, Bristol Medical School, University of Bristol, Oakfield House, Oakfield Grove, Bristol, BS8 2BN, UK
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
- NIHR Bristol Biomedical Research Centre Bristol, University Hospitals Bristol and Weston NHS Foundation Trust, University of Bristol, Bristol, UK
| | - Laura D Howe
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
- Population Health Sciences, Bristol Medical School, University of Bristol, Oakfield House, Oakfield Grove, Bristol, BS8 2BN, UK
| | - Kate M Tilling
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
- Population Health Sciences, Bristol Medical School, University of Bristol, Oakfield House, Oakfield Grove, Bristol, BS8 2BN, UK
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Zhu Y, Zhang H, Qi J, Liu Y, Yan Y, Wang T, Zeng P. Evaluating causal influence of maternal educational attainment on offspring birthweight via observational study and Mendelian randomization analyses. SSM Popul Health 2024; 25:101587. [PMID: 38229657 PMCID: PMC10790093 DOI: 10.1016/j.ssmph.2023.101587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 11/25/2023] [Accepted: 12/16/2023] [Indexed: 01/18/2024] Open
Abstract
Background Although extensive discussions on the influence of maternal educational attainment on offspring birthweight, the conclusion remains controversial, and it is challenging to comprehensively assess the causal association between them. Methods To estimate effect of maternal educational attainment on the birthweight of first child, we first conducted an individual-level analysis with UK Biobank participants of white ancestry (n = 208,162). We then implemented Mendelian randomization (MR) methods including inverse variance weighted (IVW) MR and multivariable MR to assess the causal relation between maternal education and maternal-specific birthweight. Finally, using the UK Biobank parent-offspring trio data (n = 618), we performed a polygenic score based MR to simultaneously adjust for confounding effects of fetal-specific birthweight and paternal educational attainment. We also conducted simulations for power evaluation and sensitivity analyses for horizontal pleiotropy of instruments. Results We observed that birthweight of first child was positively influenced by maternal education, with 7 years of maternal education as the reference, adjusted effect = 44.8 (95%CIs 38.0-51.6, P = 6.15 × 10-38), 54.9 (95%CIs 47.6-62.2, P = 4.21 × 10-128), and 89.4 (95%CIs 82.1-96.7, P = 4.28 × 10-34) for 10, 15 and 20 years of maternal educational attainment, respectively. A causal relation between maternal education and offspring birthweight was revealed by IVW MR (estimated effect = 0.074 for one standard deviation increase in maternal education years, 95%CIs 0.054-0.093, P = 2.56 × 10-13) and by complementary MR methods. This connection was not substantially affected by paternal education or horizontal pleiotropy. Further, we found a positive but insignificant causal association (adjusted effect = 24.0, 95%CIs -150.1-198.1, P = 0.787) between maternal education and offspring birthweight after simultaneously controlling for fetal genome and paternal education; this null causality was largely due to limited power of small sample sizes of parent-offspring trios. Conclusion This study offers supportive evidence for a causal association between maternal education and offspring birthweight, highlighting the significance of enhancing maternal education to prevent low birthweight.
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Affiliation(s)
- Yiyang Zhu
- Department of Biostatistics, School of Public Health, Xuzhou Medical University, Xuzhou, Jiangsu, 221004, China
| | - Hao Zhang
- Department of Biostatistics, School of Public Health, Xuzhou Medical University, Xuzhou, Jiangsu, 221004, China
| | - Jike Qi
- Department of Biostatistics, School of Public Health, Xuzhou Medical University, Xuzhou, Jiangsu, 221004, China
| | - Yuxin Liu
- Department of Biostatistics, School of Public Health, Xuzhou Medical University, Xuzhou, Jiangsu, 221004, China
| | - Yu Yan
- Department of Biostatistics, School of Public Health, Xuzhou Medical University, Xuzhou, Jiangsu, 221004, China
| | - Ting Wang
- Department of Biostatistics, School of Public Health, Xuzhou Medical University, Xuzhou, Jiangsu, 221004, China
| | - Ping Zeng
- Department of Biostatistics, School of Public Health, Xuzhou Medical University, Xuzhou, Jiangsu, 221004, China
- Center for Medical Statistics and Data Analysis, Xuzhou Medical University, Xuzhou, Jiangsu, 221004, China
- Key Laboratory of Human Genetics and Environmental Medicine, Xuzhou Medical University, Xuzhou, Jiangsu, 221004, China
- Key Laboratory of Environment and Health, Xuzhou Medical University, Xuzhou, Jiangsu, 221004, China
- Xuzhou Engineering Research Innovation Center of Biological Data Mining and Healthcare Transformation, Xuzhou Medical University, Xuzhou, Jiangsu, 221004, China
- Jiangsu Engineering Research Center of Biological Data Mining and Healthcare Transformation, Xuzhou Medical University, Xuzhou, Jiangsu, 221004, China
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Salvatte K, Farias DR, Normando P, Berti TL, Castro IRRD, Kac G. High Serum Folate Concentration, Vitamin B12 Deficiency, and Anthropometric Nutritional Status in Brazilian Children Aged 6-59 Months: Data from the Brazilian National Survey of Child Nutrition. J Nutr 2023; 153:2094-2104. [PMID: 37220857 DOI: 10.1016/j.tjnut.2023.05.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 05/11/2023] [Accepted: 05/19/2023] [Indexed: 05/25/2023] Open
Abstract
BACKGROUND Vitamin B12 and folate are key nutrients that help children reach their full potential in growth and development; however, little is known about the status of these vitamins in Brazilian children. OBJECTIVES To describe the serum concentrations of vitamin B12 and folate, to investigate the association between high folate concentration (HFC) and vitamin B12 deficiency, and to evaluate the association between vitamin B12 and stunting/underweight in Brazilian children aged 6-59 mo. METHODS Data from 7417 children aged 6-59 mo collected during the Brazilian National Survey on Child Nutrition were used. Serum concentrations of vitamin B12 of <150 pmol/L and folate of <10 nmol/L were classified as deficient, and folate concentrations of >45.3 nmol/L were classified as HFC. Children with length/height-for-age z-score of less than -2 were considered stunted, and those with weight-for-age z-score of less than -2 were underweight. Logistic regression models were performed. RESULTS In Brazil, 14.2% (95% CI: 12.2, 16.1) of children aged 6-59 mo had vitamin B12 deficiency, 1.1% (95% CI: 0.5, 1.6) had folate deficiency, and 36.9% (95% CI: 33.4, 40.3) had HFC. Vitamin B12 deficiency was higher in children from the northern region of Brazil (28.5%), between 6 and 24 mo (25.3%), whose mothers had lower formal education (0-7 y; 18.7%). Children with HFC had 62% lower odds (OR: 0.38; 95% CI: 0.27, 0.54) of vitamin B12 deficiency than those with normal/deficient folate. Children with vitamin B12 deficiency and normal/deficient folate had higher odds of stunting (OR: 1.58; 95% CI: 1.02, 2.43) than children without vitamin B12 deficiency and normal/deficient folate. CONCLUSIONS Vitamin B12 deficiency is a public health problem among Brazilian children aged <2 y with vulnerable socioeconomic status. HFC was inversely associated with vitamin B12 deficiency, and lower odds of stunting were observed in children with HFC and vitamin B12 deficiency than in those with vitamin B12 deficiency and normal/deficient folate.
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Affiliation(s)
- Keronlainy Salvatte
- Department of Social and Applied Nutrition, Nutritional Epidemiology Observatory, Institute of Nutrition Josué de Castro, Federal University of Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Dayana Rodrigues Farias
- Department of Social and Applied Nutrition, Nutritional Epidemiology Observatory, Institute of Nutrition Josué de Castro, Federal University of Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Paula Normando
- Department of Social and Applied Nutrition, Nutritional Epidemiology Observatory, Institute of Nutrition Josué de Castro, Federal University of Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Talita Lelis Berti
- Department of Social and Applied Nutrition, Nutritional Epidemiology Observatory, Institute of Nutrition Josué de Castro, Federal University of Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Inês Rugani Ribeiro de Castro
- Department of Social Nutrition, Nutrition Institute, State University of Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Gilberto Kac
- Department of Social and Applied Nutrition, Nutritional Epidemiology Observatory, Institute of Nutrition Josué de Castro, Federal University of Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil.
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Li H, Zhao J, Liang J, Song X. Exploring causal effects of smoking and alcohol related lifestyle factors on self-report tiredness: A Mendelian randomization study. PLoS One 2023; 18:e0287027. [PMID: 37327227 PMCID: PMC10275431 DOI: 10.1371/journal.pone.0287027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Accepted: 05/27/2023] [Indexed: 06/18/2023] Open
Abstract
Self-reported tiredness or low energy, often referred to as fatigue, has been linked to lifestyle factors, although data from randomized-controlled trials are lacking. We investigate whether modifiable lifestyle factors including smoking and alcohol intake related exposures (SAIEs) are causal factors for fatigue using Mendelian randomization (MR). A two-sample MR study was performed by using genome-wide association summary results from UK Biobank (UKBB), and each of the sample size is more than 100,000. We used the inverse variance weighted method, and sensitivity analyses (MR Egger, weighted median, penalized median estimators, and multivariable MR) to account for pleiotropy. The two-sample MR analyses showed inverse causal effect of never-smoking status and positive effect of current smoking status on the risk of fatigue. Similarly, genetically predicted alcoholic intake was positively associated with fatigue. The results were consistent across the different MR methods. Our Mendelian randomization analyses do support that the cessation of smoking and alcohol can decrease the risk of fatigue, and limit alcohol intake frequency can also reduce the risk.
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Affiliation(s)
- Heshan Li
- School of Life Sciences and Technology, Harbin Institute of Technology, Harbin, China
| | - Junru Zhao
- School of Mathematical Sciences, Harbin Engineering University, Harbin, China
| | - Jing Liang
- Harbin Huaqiang Power Automation Engineering Company Limited, Harbin, China
| | - Xiaoyu Song
- School of Life Sciences and Technology, Harbin Institute of Technology, Harbin, China
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Obeid R, Warnke I, Bendik I, Troesch B, Schoop R, Chenal E, Koletzko B. Infants' Folate Markers and Postnatal Growth in the First 4 Months of Life in Relation to Breastmilk and Maternal Plasma Folate. Nutrients 2023; 15:nu15061495. [PMID: 36986225 PMCID: PMC10051157 DOI: 10.3390/nu15061495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 02/21/2023] [Accepted: 03/15/2023] [Indexed: 03/30/2023] Open
Abstract
BACKGROUND Human milk is the sole source of folate in exclusively breastfed infants. We investigated whether human milk folate or maternal plasma folate are associated with infants' folate status and postnatal growth in the first 4 months of life. METHODS Exclusively breastfed infants (n = 120) were recruited at age < 1 month (baseline). Blood samples were available at baseline and at the age of 4 months. Plasma and breastmilk samples were available from the mothers at 8 weeks postpartum. The concentrations of (6S)-5-methyltetrahydrofolate (5-MTHF) and different folate status markers were measured in samples of the infants and their mothers. The z-scores of weight, height, and head circumference of the infants were measured five times between baseline and 4 months. RESULTS Women with 5-MTHF concentrations in breastmilk <39.9 nmol/L (median) had higher plasma 5-MTHF compared to those with milk 5-MTHF concentrations >39.9 nmol/L (mean (SD) plasma 5-MTHF = 23.3 (16.5) vs. 16.6 (11.9) nmol/L; p = 0.015). At the age of 4 months, infants of women who were higher suppliers of 5-MTHF in breastmilk had higher plasma folate than those of low-supplier women (39.2 (16.1) vs. 37.4 (22.4) nmol/L; adjusted p = 0.049). The concentrations of breastmilk 5-MTHF and maternal plasma folate were not associated with infants' longitudinal anthropometric measurements between baseline and 4 months. CONCLUSIONS Higher 5-MTHF in breastmilk was associated with higher folate status in the infants and the depletion of folate in maternal circulation. No associations were seen between maternal or breastmilk folate and infants' anthropometrics. Adaptive mechanisms might counteract the effect of low milk folate on infant development.
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Affiliation(s)
- Rima Obeid
- Department of Clinical Chemistry and Laboratory Medicine, Saarland University Hospital, D-66420 Homburg, Germany
| | - Ines Warnke
- DSM Nutritional Products Ltd., CH-4303 Kaiseraugst, Switzerland
| | - Igor Bendik
- DSM Nutritional Products Ltd., CH-4303 Kaiseraugst, Switzerland
| | - Barbara Troesch
- DSM Nutritional Products Ltd., CH-4303 Kaiseraugst, Switzerland
| | - Rotraut Schoop
- DSM Nutritional Products Ltd., CH-4303 Kaiseraugst, Switzerland
| | - Elodie Chenal
- DSM Nutritional Products Ltd., CH-4303 Kaiseraugst, Switzerland
| | - Berthold Koletzko
- Department of Paediatrics, The Ludwig Maximilian University of Munich (LMU), Dr. von Hauner Children's Hospital and LUM University Hospitals, D-80337 Munich, Germany
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