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(guó)醫(yī)學(xué)雜志》上發(fā)表的一項(xiàng)研究成果稱，全日制教育時(shí)間愈久，學(xué)生患近視的風(fēng)險(xiǎn)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，他們的研究提供了“強(qiáng)有力的證據(jù)”，證明較長(zhǎng)的受教育時(shí)間是一項(xiàng)造成近視的風(fēng)險(xiǎn)因素，該結(jié)論“對(duì)教育實(shí)踐具有重要意義”。

近視是全球范圍視力損傷的一個(gè)主要原因。目前，美國(guó)和歐洲有30%～50%成年人近視，部分東亞國(guó)家的中學(xué)畢業(yè)生中據(jù)報(bào)有80%～90%近視。

根據(jù)現(xiàn)有趨勢(shì)，到2050年，全球近視人數(shù)預(yù)計(jì)將從14億增至50億，近視將影響世界上大約一半人口。這些人中近10%（約900萬(wàn)人）將患上高度近視，失明風(fēng)險(xiǎn)更大。

許多研究報(bào)告顯示，教育與近視密切相關(guān)，但是，受教育時(shí)間增加是否會(huì)導(dǎo)致近視？近視兒童是否更加好學(xué)？社會(huì)經(jīng)濟(jì)地位是否會(huì)導(dǎo)致近視、促進(jìn)教育水平提高？——這些問(wèn)題尚無(wú)定論。

為此，布里斯托大學(xué)和卡迪夫大學(xué)的研究人員開(kāi)始著手調(diào)查：教育是否是導(dǎo)致近視的直接因素，而近視又是否是增加教育時(shí)長(zhǎng)的誘因。

研究人員采用孟德?tīng)栯S機(jī)化法，在英國(guó)生物銀行數(shù)據(jù)庫(kù)中挑選40到69歲間的67798名男性和女性，分析了44個(gè)與近視相關(guān)的基因變體和69個(gè)與學(xué)校教育時(shí)長(zhǎng)相關(guān)的基因變體。

以這種方式分析基因信息可以避免一些困擾傳統(tǒng)觀察研究的問(wèn)題，不易受到無(wú)法測(cè)量（混淆）因素的干擾，所以研究結(jié)果可能更為可靠。

因此，采用孟德?tīng)栯S機(jī)化法所觀察到的關(guān)聯(lián)更加證明了因果關(guān)系的推斷。

在考慮潛在影響因素的基礎(chǔ)上，孟德?tīng)栯S機(jī)化分析表明，受教育時(shí)間每增加一年，近視也會(huì)隨之加深一點(diǎn)點(diǎn)（屈光度誤差為每年0.27度）。

具體來(lái)說(shuō)，一個(gè)接受17年教育的英國(guó)大學(xué)畢業(yè)生一般會(huì)比接受12年教育就離開(kāi)學(xué)校的16歲少年近視至少深1度。近視達(dá)到這種程度，就意味著駕駛時(shí)需要戴眼鏡。

相比之下，幾乎沒(méi)有證據(jù)顯示，近視促使人們接受更長(zhǎng)時(shí)間的教育。

研究人員提出了一些研究局限。例如，與英國(guó)一般人群相比，英國(guó)生物銀行參與者的受教育程度更高、生活方式更健康、提交的健康問(wèn)題也更少——這些都可能影響研究結(jié)果。然而，并沒(méi)有什么證據(jù)表明這些因素與研究結(jié)果存在聯(lián)系。

他們總結(jié)認(rèn)為：“該研究表明，隨著教育時(shí)長(zhǎng)增加，近視更加普遍;研究還強(qiáng)調(diào)，有必要進(jìn)一步研究討論如何改善教育實(shí)踐，在提高教育成果的同時(shí)，避免對(duì)視力產(chǎn)生不利影響?！?/p>

在一篇相關(guān)的社論中，澳大利亞國(guó)立大學(xué)的伊恩·摩根教授及其同事指出，有證據(jù)表明，除了基因，環(huán)境和社會(huì)因素也可能對(duì)近視產(chǎn)生重大影響。

他們提到東亞地區(qū)，那兒的早期教育壓力強(qiáng)度大，戶外游戲時(shí)間少，小學(xué)畢業(yè)的近視兒童幾乎達(dá)到50%，相比之下，對(duì)英國(guó)兒童的研究則顯示，近視兒童不到10%。

他們提醒道：“近視產(chǎn)生得早，意味著會(huì)有更多時(shí)間發(fā)展成高度近視和潛在病理性近視?！彼麄冋J(rèn)為，“必須調(diào)整”教育系統(tǒng)，“以幫助保護(hù)后代的視力健康”。

研究作者丹尼斯·阿塔也在一篇相關(guān)的評(píng)論文章中指出，有證據(jù)顯示，兒童時(shí)期常在戶外活動(dòng)，可以在一定程度上防止近視。

對(duì)于教育與近視的關(guān)聯(lián)，與自然光接觸的減少可能不是唯一的解釋，但她寫道：“鑒于戶外活動(dòng)對(duì)精神健康的益處、對(duì)肥胖癥以及慢性疾病的預(yù)防作用，在戶外消磨更多時(shí)間可能會(huì)給我們各方面都帶來(lái)好處?！?/p>

（譯者單位：上海外國(guó)語(yǔ)大學(xué)）