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Association between birth weight and educational attainment: an individual-based pooled analysis of nine twin cohorts
  1. Aline Jelenkovic1,2,
  2. Janne Mikkonen1,
  3. Pekka Martikainen1,
  4. Antti Latvala3,
  5. Yoshie Yokoyama4,
  6. Reijo Sund1,5,
  7. Eero Vuoksimaa3,
  8. Esther Rebato2,
  9. Joohon Sung6,7,
  10. Jina Kim6,
  11. Jooyeon Lee6,
  12. Sooji Lee6,
  13. Maria A Stazi8,
  14. Corrado Fagnani8,
  15. Sonia Brescianini8,
  16. Catherine A Derom9,10,
  17. Robert F Vlietinck9,
  18. Ruth J F Loos11,
  19. Robert F Krueger12,
  20. Matt McGue12,
  21. Shandell Pahlen12,
  22. Tracy L Nelson13,
  23. Keith E Whitfield14,
  24. Ingunn Brandt15,
  25. Thomas S Nilsen15,
  26. Jennifer R Harris15,
  27. Tessa L Cutler16,
  28. John L Hopper6,16,
  29. Adam D Tarnoki17,18,
  30. David L Tarnoki17,18,
  31. Thorkild I A Sørensen19,20,
  32. Jaakko Kaprio3,21,
  33. Karri Silventoinen1,22
  1. 1Department of Social Research, University of Helsinki, Helsinki, Finland
  2. 2Department of Genetics, Physical Anthropology and Animal Physiology, University of the Basque Country UPV/EHU, Leioa, Spain
  3. 3Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland
  4. 4Department of Public Health Nursing, Osaka City University, Osaka, Japan
  5. 5Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland
  6. 6Department of Epidemiology, School of Public Health, Seoul National University, Seoul, The Republic of Korea
  7. 7Institute of Health and Environment, Seoul National University, Seoul, The Republic of Korea
  8. 8Centre for Behavioural Sciences and Mental Health, Istituto Superiore di Sanità, Rome, Italy
  9. 9Centre of Human Genetics, University Hospitals Leuven, Leuven, Belgium
  10. 10Department of Obstetrics and Gynaecology, Ghent University Hospitals, Ghent, Belgium
  11. 11The Charles Bronfman Institute for Personalized Medicine, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York City, New York, USA
  12. 12Department of Psychology, University of Minnesota, Minneapolis, Minnesota, USA
  13. 13Department of Health and Exercise Sciencies and Colorado School of Public Health, Colorado State University, Fort Collins, Colorado, USA
  14. 14Department of Psychology and Neuroscience, Duke University, Durham, North Carolina, USA
  15. 15Department of Genes and Environment, Norwegian Institute of Public Health, Oslo, Norway
  16. 16The Australian Twin Registry, Centre for Epidemiology and Biostatistics, The University of Melbourne, Melbourne, Victoria, Australia
  17. 17Department of Radiology, Semmelweis University, Budapest, Hungary
  18. 18Hungarian Twin Registry, Budapest, Hungary
  19. 19Novo Nordisk Foundation Centre for Basic Metabolic Research (Section of Metabolic Genetics), Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
  20. 20Department of Public Health (Section of Epidemiology), Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
  21. 21Department of Public Health, University of Helsinki, Helsinki, Finland
  22. 22Osaka University Graduate School of Medicine, Osaka University, Osaka, Japan
  1. Correspondence to Dr Aline Jelenkovic, Population Research Unit, Department of Social Research, University of Helsinki, Helsinki 00014, Finland; aline.jelenkovic{at}helsinki.fi

Abstract

Background There is evidence that birth weight is positively associated with education, but it remains unclear whether this association is explained by familial environmental factors, genetic factors or the intrauterine environment. We analysed the association between birth weight and educational years within twin pairs, which controls for genetic factors and the environment shared between co-twins.

Methods The data were derived from nine twin cohorts in eight countries including 6116 complete twin pairs. The association between birth weight and educational attainment was analysed both between individuals and within pairs using linear regression analyses.

Results In between-individual analyses, birth weight was not associated with educational years. Within-pairs analyses revealed positive but modest associations for some sex, zygosity and birth year groups. The greatest association was found in dizygotic (DZ) men (0.65 educational years/kg birth weight, p=0.006); smaller effects of 0.3 educational years/kg birth weight were found within monozygotic (MZ) twins of both sexes and opposite-sex DZ twins. The magnitude of the associations differed by birth year in MZ women and opposite-sex DZ twins, showing a positive association in the 1915–1959 birth cohort but no association in the 1960–1984 birth cohort.

Conclusion Although associations are weak and somewhat inconsistent, our results suggest that intrauterine environment may play a role when explaining the association between birth weight and educational attainment.

  • birth weight
  • education
  • twins/genetics

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Footnotes

  • Contributors YY, TIAS, JKa and KS planned the study design of the CODATwins project. YY, JS, JKi, JL, SL, MAS, CF, SB, CAD, RFV, RJFL, RFK, MM, SP, TLN, KEW, IB, TSN, JRH, TLC, JLH, ADT, DLT and JKa collected the data used in this study. AJ and KS were in charge of data management. RS provided statistical advice. AJ conducted the analyses and wrote the first draft of the manuscript. All authors have commented on the manuscript and read and approved the final version of the manuscript.

  • Funding This work was supported by the Academy of Finland (grant #266592). The Australian Twin Registry is supported by a Centre of Research Excellence (grant ID 1079102) from the National Health and Medical Research Council administered by the University of Melbourne. The Carolina African American Twin Study of Aging (CAATSA) was funded by a grant from the National Institute on Aging (grant 1RO1-AG13662-01A2) to KEW. Since its origin the East Flanders Prospective Survey has been partly supported by grants from the Fund of Scientific Research, Flanders and Twins, a non-profit Association for Scientific Research in Multiple Births (Belgium). Data collection and analyses in Finnish twin cohorts have been supported by ENGAGE – European Network for Genetic and Genomic Epidemiology, FP7-HEALTH-F4-2007, grant agreement number 201413, National Institute of Alcohol Abuse and Alcoholism (grants AA-12502, AA-00145, and AA-09203 to R J Rose, the Academy of Finland Center of Excellence in Complex Disease Genetics (grant numbers: 213506, 129680), and the Academy of Finland (grants 100499, 205585, 118555, 141054, 265240, 263278 and 264146 to J Kaprio). Anthropometric measurements of the Hungarian twins were supported by Medexpert Ltd., Budapest, Hungary. Korean Twin-Family Register was supported by the Global Research Network Program of the National Research Foundation (NRF 2011-220-E00006).

  • Competing interests None declared.

  • Patient consent Not required.

  • Ethics approval Ethical committee of the Department of Public Health, University of Helsinki.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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