Education Linked to Higher Risk of Short-sightedness教育與近視

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 .《英國醫學雜志》上發表的一項研究成果稱，全日制教育時間愈久，學生患近視的風險愈大。

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“強有力的證據”，證明較長的受教育時間是一項造成近視的風險因素，該結論“對教育實踐具有重要意義”。

近視是全球范圍視力損傷的一個主要原因。目前，美國和歐洲有30%～50%成年人近視，部分東亞國家的中學畢業生中據報有80%～90%近視。

根據現有趨勢，到2050年，全球近視人數預計將從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900萬人）將患上高度近視，失明風險更大。

許多研究報告顯示，教育與近視密切相關，但是，受教育時間增加是否會導致近視？近視兒童是否更加好學？社會經濟地位是否會導致近視、促進教育水平提高？——這些問題尚無定論。

為此，布里斯托大學和卡迪夫大學的研究人員開始著手調查：教育是否是導致近視的直接因素，而近視又是否是增加教育時長的誘因。

研究人員采用孟德爾隨機化法，在英國生物銀行數據庫中挑選40到69歲間的67798名男性和女性，分析了44個與近視相關的基因變體和69個與學校教育時長相關的基因變體。

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

因此，采用孟德爾隨機化法所觀察到的關聯更加證明了因果關系的推斷。

在考慮潛在影響因素的基礎上，孟德爾隨機化分析表明，受教育時間每增加一年，近視也會隨之加深一點點（屈光度誤差為每年0.27度）。

具體來說，一個接受17年教育的英國大學畢業生一般會比接受12年教育就離開學校的16歲少年近視至少深1度。近視達到這種程度，就意味著駕駛時需要戴眼鏡。

相比之下，幾乎沒有證據顯示，近視促使人們接受更長時間的教育。

研究人員提出了一些研究局限。例如，與英國一般人群相比，英國生物銀行參與者的受教育程度更高、生活方式更健康、提交的健康問題也更少——這些都可能影響研究結果。然而，并沒有什么證據表明這些因素與研究結果存在聯系。

他們總結認為：“該研究表明，隨著教育時長增加，近視更加普遍;研究還強調，有必要進一步研究討論如何改善教育實踐，在提高教育成果的同時，避免對視力產生不利影響。”

在一篇相關的社論中，澳大利亞國立大學的伊恩·摩根教授及其同事指出，有證據表明，除了基因，環境和社會因素也可能對近視產生重大影響。

他們提到東亞地區，那兒的早期教育壓力強度大，戶外游戲時間少，小學畢業的近視兒童幾乎達到50%，相比之下，對英國兒童的研究則顯示，近視兒童不到10%。

他們提醒道：“近視產生得早，意味著會有更多時間發展成高度近視和潛在病理性近視。”他們認為，“必須調整”教育系統，“以幫助保護后代的視力健康”。

研究作者丹尼斯·阿塔也在一篇相關的評論文章中指出，有證據顯示，兒童時期常在戶外活動，可以在一定程度上防止近視。

對于教育與近視的關聯，與自然光接觸的減少可能不是唯一的解釋，但她寫道：“鑒于戶外活動對精神健康的益處、對肥胖癥以及慢性疾病的預防作用，在戶外消磨更多時間可能會給我們各方面都帶來好處。”

（譯者單位：上海外國語大學）