Education linked to higher risk of short-sightedness

Spending more years in full time education is associated with a greater risk of developing short-sightedness (myopia), finds a study published by The BMJ that used genetic data for 67,798 participants of UK Biobank. The researchers say their study provides “strong evidence” that more time spent in education is a risk factor for myopia, and that the findings “have important implications for educational practices.”

Myopia, or short-sightedness, is a leading cause of visual impairment worldwide. Currently, 30-50% of adults in the United States and Europe are myopic, with levels of 80-90% reported in school leavers in some East Asian countries. Based on existing trends, the number of people affected by myopia worldwide is expected to increase from 1.4 billion to 5 billion by 2050, affecting about half of the world’s population. Almost 10% of these people (around 9 million) will have high myopia, which carries a greater risk of blindness. Many studies have reported strong links between education and myopia, but it is not clear whether increasing exposure to education causes myopia, myopic children are more studious, or socioeconomic position leads to myopia and higher levels of education.

So researchers based at the University of Bristol and Cardiff University set out to determine whether education is a direct (causal) risk factor for myopia, or myopia is a causal risk factor for more years in education. Using a technique called Mendelian randomisation, they analysed 44 genetic variants associated with myopia and 69 genetic variants associated with years of schooling for men and women aged 40 to 69 years from the UK Biobank database.

After taking account of potentially influential factors, Mendelian randomisation analyses suggested that every additional year of education was associated with more myopia (a refractive error of −0.27 dioptres a year). To put this into context, a university graduate from the UK with 17 years of education would, on average, be at least −1 dioptre more myopic than someone who left school at 16 (with 12 years of education). This level of myopia would mean needing glasses for driving.

In a linked editorial, Professor Ian Morgan at the Australian National University and colleagues say the evidence suggests that it is not only genes but environmental and social factors that may have major effects on myopia. Researchers point to East Asia, where early intense educational pressures combined with little time for play outdoors has led to almost 50% of children being myopic by the end of primary school, compared with less than 10% in a study of British children.