Every year spent in education increases short sightedness, reveals new study
5 September 2017
A recent study carried out by researchers at the MRC IEU has discovered a causal link between time spent in education and short sightedness. This finding suggest that current educational practices are leading to an increased incidence of short sightedness and this may have important implications for education policy.
Short sightedness or myopia is the leading cause of visual disability across the globe and is rapidly rising in prevalence. Currently, 50% of adults in the US and Europe are myopic and in Southeast Asia myopia has reached epidemic levels. Myopia occurs when light is refracted incorrectly in the eye leading to poor long-distance vision. Myopia is highly heritable, but can also be caused by early visual experiences.
The study found that every additional year spent in education increased the severity of myopia. In addition, the researchers found that being short sighted did not increase educational attainment or time spent in education, ruling out reverse causality.
The researchers used bidirectional Mendelian Randomisation (MR) to investigate the effect of education on myopia. Bidirectional MR is a technique used in epidemiology which tests for a causal link between factors in both directions and can therefore reveal which factor is causing a change in the other well as whether the link is causal.
This study provides evidence that correlations previously shown between myopia and education from observational studies are in fact causal. Interestingly, the effect found in this study was even greater than has been previously estimated. This may mean that confounding factors present in observational studies, such as socioeconomic status, may have been masking the true size of the effect.
How education causes myopia is not yet clear, although there is evidence that spending more time outdoors can help prevent development of myopia in children. It is possible that more highly educated individuals spend less time outside during and/or after education and this may explain why myopia is more common. There is currently no consistent evidence that work-related activities such as reading cause myopia to develop in children.
The study utilised genetic elements robustly associated with myopia and educational attainment from large samples of participants (nearly 70,000 individuals) collected as part of the UK Biobank project between 2006 and 2010.
This paper is part of an ongoing study available on Biorxiv: http://www.biorxiv.org/content/early/2017/08/04/172247