Better educated people are 'more likely to be short-sighted'
Better educated people really are more likely to be short-sighted, according to new research.
Boffins and brainboxes - such as Egon Spengler from Ghostbusters and Brains in Thunderbirds - are traditionally portrayed as wearing glasses.
Now a new study, published by The BMJ, shows that spending more years in full time education is associated with a greater risk of developing short-sightedness, also known as myopia.
The researchers say their findings provide 'strong evidence' that more time spent in education is a risk factor for myopia, and 'have important implications for educational practices.'
Myopia is a leading cause of visual impairment worldwide. Currently, 30 to 50 per cent of adults in Europe and the United States are myopic, with levels of 80 to 90 per cent 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 five billion by 2050, affecting about half of the world's population.
Almost 10 per cent of these people - around nine 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 socio-economic position leads to myopia and higher levels of education.
Researchers based at the University of Bristol and Cardiff University set out to determine whether education is a direct, or 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 67,798 men and women aged 40 to 69 from the UK Biobank database.
The researchers said that analysing genetic information in such a way avoids some of the problems that afflict traditional observational studies, making the results less prone to unmeasured factors, and therefore more likely to be reliable.
An association that is observed using Mendelian randomisation therefore strengthens the inference of a causal relationship.
After taking account of potentially influential factors, Mendelian randomisation analyses suggested that every additional year of education was associated with more myopia.
To put that into context, a British university graduate with 17 years of education would, on average, be at least âˆ’1 dioptre more myopic than someone who left school at 16 with 12 years of education. That level of myopia would mean needing glasses for driving.
By contrast, there was little evidence to suggest that myopia led people to remain in education for longer.
The researchers point to some study limitations. For example, UK Biobank participants have been shown to be more highly educated, have healthier lifestyles, and report fewer health issues compared with the general UK population.
But there was little evidence that could explain their findings.
Study author Dr Denize Atan, of Bristol University, said: 'This study shows that exposure to more years in education contributes to the rising prevalence of myopia, and highlights a need for further research and discussion about how educational practices might be improved to achieve better outcomes without adversely affecting vision."
Dr Atan also pointed to evidence showing that time spent outdoors in childhood partially protects against the development of myopia.
Although reduced exposure to natural daylight might not be the sole mechanism to explain the association between education and myopia, she said: "Given the advantages of time spent outdoors on mental health and the protection it provides against obesity and chronic diseases, we might all benefit from spending more time outside.'
Commenting on the findings, 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.
They point to East Asia, where early intense educational pressures combined with little time for play outdoors has led to almost 50 per cent of children being myopic by the end of primary school, compared with less than 10 per cent in a study of British children.
Prof Morgan added: 'Early onset allows more time for myopia to progress to high and potentially pathological myopia."
He warned that education systems 'must change to help protect the visual health of future generations.'