In the UK, the clocks go back by one hour on Sunday to mark the end of British Summer Time. Experts have been weighing up a more permanent time shift in our daily schedules, particularly for tired teenagers who struggle with early school starts.

每年入冬时，英国把时钟往后拨1个小时，这标志着夏令时结束。专家们在考虑对我们的日常作息时间作出更为永久性的调整，特别是针对那些艰难应对大清早上学的没睡醒的青少年。

The rethink on teen slumber¹ is largely due to the emerging science on circadian rhythms. The genetics associated with body clocks earned this year's Nobel Prize for physiology² or medicine. The timing³ of release of the sleep hormone⁴ melatonin is thought to change with age: during adolescence⁵, secretion⁶ begins late at night and continues until about 8am. The sleep rhythm of a teenager can lag an adult by two to three hours.

重新思考青少年的睡眠问题，在很大程度上是因为新兴的昼夜节律科学。与生物钟有关的基因研究赢得了今年的诺贝尔生理学或医学奖(Nobel Prize for physiology or medicine)。人体释放睡眠荷尔蒙--褪黑激素的时间据信会随着年龄改变：在青春期，褪黑激素在深夜开始释放并持续到早上8点左右。青少年的睡眠节律可能比成年人晚两到三个小时。

A report by the Rand Corporation argues that, for adolescents, delaying the start of school to 8.30am or later could bring a $140bn benefit to the US economy over 15 years. Some US school days start as early as 7am.

兰德公司(Rand Corporation)的一份报告认为，把青少年的上学时间推迟到8点30分或更晚，有望在未来15年给美国经济带来1400亿美元的效益。美国一些学校早上7点就开始上课了。

The gains, which amount to a dividend⁷ of $9.3bn a year, arise mainly from two predicted pay-offs: improved academic performance, which increases the likelihood of graduation and future work; and a reduction in car crashes, which means more students make it into the future labour supply.

这项收益--相当于每年93亿美元--主要来自两个预计回报：一是学习成绩提高，从而增加毕业和未来就业的可能性;二是车祸事故减少，这意味着会有更多学生安好地加入未来的劳动力队伍。

Marco Hafner, a Rand economist⁸, says the gains could be even higher because the calculation of benefits were on the conservative side. The input⁹ to the macroeconomic simulation did not factor in other phenomena¹⁰, such as the risks of suicide and obesity¹¹ that are believed to be exacerbated¹² by sleep deprivation¹³.

兰德的经济学家马尔科?哈夫纳(Marco Hafner)表示，因为计算效益时偏向保守，所以实际效益可能更高。宏观经济模拟的输入没有考虑其他现象，比如自杀和肥胖风险--据信睡眠不足会加剧这类风险。

Rand, which used data from 47 US states, concluded that teenage sleep deprivation should be regarded as an economic problem with a possible solution. The financial rewards, it says, would quickly outweigh¹⁴ any associated costs of fixing it, such as rescheduling bus routes or extending after-school clubs.

兰德利用美国47个州的数据得出结论认为，青少年睡眠不足应该被视为一个可能解决的经济问题。该公司表示，经济回报将很快超过解决该问题的相关成本，比如重新安排公交车时间表，或延长课外兴趣小组的时间。

There have been concerns about "insufficient¹⁵ sleep" among adolescents - the recommendation is between eight and 10 hours per night - for some time in the US.

在美国，各方担忧青少年"睡眠不足"--建议每晚睡眠8-10个小时--已经有一段时间了。

In 2014, the American Academy of Paediatrics published a policy statement recognising "insufficient sleep in adolescents as an important public health issue that significantly affects the health and safety, as well as the academic success, of our nation's middle and high school students".

2014年，美国儿科学会(American Academy of Pediatrics)发表政策声明，承认"青少年睡眠不足是一个重要的公共卫生问题，对我国初中和高中学生的健康和安全、以及学习成绩有显著影响"。

Trials of delayed school start times have shown benefits such as increased sleep (children seem to go to bed at the same time but wake later), increased alertness, higher attendance and better mood. This led the academy to give its unequivocal backing for change.

推迟上学时间的试验已经展现了一些好处，比如睡眠时间增加(孩子们似乎会在同样的时间睡觉，但起床时间更晚)、思维更加敏捷、出勤率提高以及情绪更好。这使得美国儿科学会明确支持这项改革。

Last month, however, a bill designed to enact¹⁶ such a change faltered¹⁷ in California. The bill, which has the backing of the Start School Later movement, a lobby group of parents, health professionals and policymakers, is likely to resurface in January. Many schools in other states have already acted.

然而，旨在落实这一改革的法案最近在加利福尼亚州不了了之。该法案得到了由家长、健康专家和政策制定者组成的游说组织"晚点上学"(Start School Later)运动的支持，有可能2018年1月重新出炉。其他州的很多学校已经采取行动。

All the evidence points to teen sleeping patterns being a consequence¹⁸ of biology, not attitude, according to Kyla Wahlstrom, an educational policy specialist at the University of Minnesota, who has studied this issue since 1996.

明尼苏达大学(University of Minnesota)的教育政策专家、从1996年开始研究该问题的凯拉?瓦尔斯特龙(Kyla Wahlstrom)表示，所有证据都表明青少年睡眠规律是生理学(而非态度)造成的。

Delayed start times, Dr Wahlstrom says, have immediate¹⁹ and noticeable impacts, such as a reduced rate of teenage car crashes. One county in Kentucky saw the number of teenage crashes fall by 16 per cent in the two years after school starts were delayed by an hour, a reduction attributed to the drivers being more alert. The crash rate rose by 8 per cent across the state as a whole.

瓦尔斯特龙博士表示，推迟上学时间可以带来立即而明显的影响，比如青少年车祸率降低。在把上学时间推迟一个小时后，肯塔基州某县两年期间的青少年车祸数量减少了16%，这被归因于司机的精神更集中。同期肯塔基州全州的车祸增加了8%。

As well as the AAP, the American Medical Association and the Centers for Disease Control in the US, support such a change. About 250 US schools are thought to have redesigned their schedules to accommodate the recommendations.

与美国儿科学会一样，美国医学会(American Medical Association)和美国疾病控制预防中心(Centers for Disease Control)也支持这一改革。据信全美已有大约250所学校为落实相关建议而重新设计了课程表。

A similar debate has been stirring in the UK. In 2015, Paul Kelley, a professor at the Sleep and Circadian Neuroscience Institute at Oxford²⁰ university, suggested that 16-year-olds should start no earlier than 10am. For 18-year-olds, an 11am start is preferable. Early starts, he says, mean pupils are usually performing suboptimally.

类似辩论也在英国升温。2015年，牛津大学(University of Oxford)睡眠和昼夜节律神经科学研究所(Sleep and Circadian Neuroscience Institute)教授保罗?凯利(Paul Kelley)建议，16岁学生的上学时间不应早于上午10点。对于18岁的学生，11点上学更好。他表示，过早上学通常意味着学生表现欠佳。

Not everyone concurs²¹: scientists at the universities of Surrey and Harvard dispute that delayed starts will lead to teenagers getting more sleep. One unintended consequence, for example, might be students being exposed to artificial light for longer because of later bedtimes.

并非所有人都同意该结论：萨里大学(Surrey University)和哈佛大学(Harvard University)的科学家质疑推迟上学时间将导致青少年睡眠时间增加的结论。例如，一个意外后果可能是因为上床睡觉时间推迟，学生们暴露在人造灯光下的时间更长。

Based on mathematical modelling, this contrary study suggested that turning down the lights in the evening would allow teenagers to get more sleep without the need for a change to the school day. The time that students spend on their mobile phones and other devices also crops up regularly as a complicating²² factor in teenage sleep studies.

这项相反的研究基于数学建模，它似乎表明，晚上早些关灯就可以让青少年的睡眠时间增加，而无需改变上学时间。在青少年睡眠研究中，学生们花在手机及其他设备上的时间也经常会冒出来，成为一个使问题复杂化的因素。

Nevertheless, one London head of an independent school has chosen to push back the start of the day for sixth-formers to 9.30am. Explaining his decision in an article for the Times Educational Supplement, Jonathan Taylor pointed²³ out that the 9-to-5 mode of working was disappearing anyhow. He criticised educators who clung to an early start out of "a misguided notion of traditional self-discipline?.?.?.?is it really more worthy²⁴ to learn maths at 8.30am than 5pm?"

尽管如此，伦敦一家私立学校的校长选择把高中生的上学时间推迟到早上9点30分。乔纳森?泰勒(Jonathan Taylor)在为《泰晤士报教育增刊》(Times Educational Supplement)撰写的文章中解释了自己的决定，他指出，朝九晚五的工作模式反正将要终结。他指责那些坚持早上学的教育家是出于"自律这种具有误导性的传统理念……难道早上8点30分学数学，就一定比下午5点学数学更有价值吗?"

Attendance and punctuality, Mr Taylor enthused, had improved - and the teenagers made for jollier company. Heaven knows, we could all do with happier teens.

泰勒兴奋地表示，推迟上学时间后，学生的出勤率提高，迟到率下降，而且青少年们更容易相处了。天知道，我们都需要更快乐的青少年。