Education Linked to Higher Risk of Short-sightedness教育与近视

唐一辰

Spending more years in full time education is associated with a greater risk of developing short-sightedness （myopia1）， finds a study published by The BMJ .《英國医学杂志》上发表的一项研究成果称，全日制教育时间愈久，学生患近视的风险愈大。

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 impairment2 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 randomisation3， 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 years from the UK Biobank database.

Analysing genetic information in this way avoids some of the problems that afflict4 traditional observational studies， making the results less prone to unmeasured （confounding） factors， and therefore more likely to be reliable.

An association that is observed using Mendelian randomisation therefore strengthens the inference5 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 （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.

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， which may have affected the results. However， there was little evidence that this could explain their findings.

“This study shows that exposure to more years in education contributes to the rising prevalence6 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，” they conclude.

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.

They 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.

“Early onset7 allows more time for myopia to progress to high and potentially pathological8 myopia，” they warn， and they argue that education systems “must change to help protect the visual health of future generations.”

In a linked opinion piece， study author Denize Atan also points 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 writes， “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.”

研究人員表示，他们的研究提供了“强有力的证据”，证明较长的受教育时间是一项造成近视的风险因素，该结论“对教育实践具有重要意义”。

近视是全球范围视力损伤的一个主要原因。目前，美国和欧洲有30%～50%成年人近视，部分东亚国家的中学毕业生中据报有80%～90%近视。

根据现有趋势，到2050年，全球近视人数预计将从14亿增至50亿，近视将影响世界上大约一半人口。这些人中近10%（约900万人）将患上高度近视，失明风险更大。

许多研究报告显示，教育与近视密切相关，但是，受教育时间增加是否会导致近视？近视儿童是否更加好学？社会经济地位是否会导致近视、促进教育水平提高？——这些问题尚无定论。

为此，布里斯托大学和卡迪夫大学的研究人员开始着手调查：教育是否是导致近视的直接因素，而近视又是否是增加教育时长的诱因。

研究人员采用孟德尔随机化法，在英国生物银行数据库中挑选40到69岁间的67798名男性和女性，分析了44个与近视相关的基因变体和69个与学校教育时长相关的基因变体。

以这种方式分析基因信息可以避免一些困扰传统观察研究的问题，不易受到无法测量（混淆）因素的干扰，所以研究结果可能更为可靠。

因此，采用孟德尔随机化法所观察到的关联更加证明了因果关系的推断。

在考虑潜在影响因素的基础上，孟德尔随机化分析表明，受教育时间每增加一年，近视也会随之加深一点点（屈光度误差为每年0.27度）。

具体来说，一个接受17年教育的英国大学毕业生一般会比接受12年教育就离开学校的16岁少年近视至少深1度。近视达到这种程度，就意味着驾驶时需要戴眼镜。

相比之下，几乎没有证据显示，近视促使人们接受更长时间的教育。

研究人员提出了一些研究局限。例如，与英国一般人群相比，英国生物银行参与者的受教育程度更高、生活方式更健康、提交的健康问题也更少——这些都可能影响研究结果。然而，并没有什么证据表明这些因素与研究结果存在联系。

他们总结认为：“该研究表明，随着教育时长增加，近视更加普遍;研究还强调，有必要进一步研究讨论如何改善教育实践，在提高教育成果的同时，避免对视力产生不利影响。”

在一篇相关的社论中，澳大利亚国立大学的伊恩·摩根教授及其同事指出，有证据表明，除了基因，环境和社会因素也可能对近视产生重大影响。

他们提到东亚地区，那儿的早期教育压力强度大，户外游戏时间少，小学毕业的近视儿童几乎达到50%，相比之下，对英国儿童的研究则显示，近视儿童不到10%。

他们提醒道：“近视产生得早，意味着会有更多时间发展成高度近视和潜在病理性近视。”他们认为，“必须调整”教育系统，“以帮助保护后代的视力健康”。

研究作者丹尼斯·阿塔也在一篇相关的评论文章中指出，有证据显示，儿童时期常在户外活动，可以在一定程度上防止近视。

对于教育与近视的关联，与自然光接触的减少可能不是唯一的解释，但她写道：“鉴于户外活动对精神健康的益处、对肥胖症以及慢性疾病的预防作用，在户外消磨更多时间可能会给我们各方面都带来好处。”

（译者单位：上海外国语大学）