Education and myopia: assessing the direction of causality by mendelian randomisation

Mountjoy, Edward, Davies, Neil M., Plotnikov, Denis, Davey Smith, George, Rodriguez, Santiago, Williams, Cathy E., Guggenheim, Jeremy A ORCID: https://orcid.org/0000-0001-5164-340X and Atan, Denize 2018. Education and myopia: assessing the direction of causality by mendelian randomisation. BMJ 361 , k2022. 10.1136/bmj.k2022

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Abstract

Objectives To determine whether more years spent in education is a causal risk factor for myopia, or whether myopia is a causal risk factor for more years in education. Design Bidirectional, two sample mendelian randomisation study. Setting Publically available genetic data from two consortiums applied to a large, independent population cohort. Genetic variants used as proxies for myopia and years of education were derived from two large genome wide association studies: 23andMe and Social Science Genetic Association Consortium (SSGAC), respectively. Participants 67 798 men and women from England, Scotland, and Wales in the UK Biobank cohort with available information for years of completed education and refractive error. Main outcome measures Mendelian randomisation analyses were performed in two directions: the first exposure was the genetic predisposition to myopia, measured with 44 genetic variants strongly associated with myopia in 23andMe, and the outcome was years in education; and the second exposure was the genetic predisposition to higher levels of education, measured with 69 genetic variants from SSGAC, and the outcome was refractive error. Results Conventional regression analyses of the observational data suggested that every additional year of education was associated with a more myopic refractive error of −0.18 dioptres/y (95% confidence interval −0.19 to −0.17; P<2e-16). Mendelian randomisation analyses suggested the true causal effect was even stronger: −0.27 dioptres/y (−0.37 to −0.17; P=4e-8). By contrast, there was little evidence to suggest myopia affected education (years in education per dioptre of refractive error −0.008 y/dioptre, 95% confidence interval −0.041 to 0.025, P=0.6). Thus, the cumulative effect of more years in education on refractive error means that a university graduate from the United Kingdom with 17 years of education would, on average, be at least −1 dioptre more myopic than someone who left school at age 16 (with 12 years of education). Myopia of this magnitude would be sufficient to necessitate the use of glasses for driving. Sensitivity analyses showed minimal evidence for genetic confounding that could have biased the causal effect estimates. Conclusions This study shows that exposure to more years in education contributes to the rising prevalence of myopia. Increasing the length of time spent in education may inadvertently increase the prevalence of myopia and potential future visual disability.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Advanced Research Computing @ Cardiff (ARCCA) Optometry and Vision Sciences
Publisher:	BMJ Publishing Group
ISSN:	1759-2151
Funders:	Medical Research Council, Bristol Centre for Systems Biomedicine, Global Education Program of the Russian Federation government, National Eye Research Centre, NIHR, Economics and Social Research Council
Date of First Compliant Deposit:	8 May 2018
Date of Acceptance:	19 April 2018
Last Modified:	07 May 2023 09:12
URI:	https://orca.cardiff.ac.uk/id/eprint/111260

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