When you curl up in bed, consider reading an old-fashioned printed book rather than a smartphone or tablet. Your sleep should be deeper and more restful. That’s the finding of a study in the Proceedings of the National Academy of Sciences.

当你蜷缩在床上，考虑读一本传统的纸质书而不是浏览智能手机或平板电脑，那你的睡眠应该会更深、更宁静。这项研究结果出自《美国国家科学院院刊》。

Researchers had 12 healthy young adults read either a printed book or an iPad for four hours before bed during five consecutive evenings. During the fifth night blood samples were collected every hour via an IV during both the reading and sleeping periods. The research team assessed sleep time and REM cycles, and the subjects self-rated their sleepiness every evening and morning. All participants read for five nights on the iPad and for five from a book.

研究人员请来 12位健康的年轻人，让他们连续五个晚上，每晚睡前要么读四小时纸质书要么读四小时平板电脑。第五天通过静脉注射，分别于阅读和睡眠期间每小时抽取一次血液样本。研究团队会评估受试者的睡眠时间和睡眠周期，受试者每天早晚也要做睡眠自评。所有的受试者都连续读了五晚的平板电脑或纸质书。

As anticipated, reading print made for better Zzzs. Participants reading the iPad took about 10 minutes longer to fall asleep, secreted less sleep-inducing melatonin, and shifted their internal circadian clock. They also reported feeling more tired the next morning.

不出所料，阅读纸质书的人能更安心的呼呼大睡。那些阅读平板电脑的受试者大约多花 10分钟才能入睡，睡眠中分泌的褪黑激素也比较少，还影响了他们内在的生物钟。同时他们还报告说第二天早晨会感觉更累。

The study’s first author, Anne-Marie Chang, then of Boston’s Brigham and Women’s Hospital, says that devices like the original Kindle, that do not produce their own light, should likely still be a good choice for bedtime reading. But when it comes to those backlit gadgets, probably best to read those over your morning coffee.

这项研究的第一作者——波士顿布莱根妇女医院的安妮-玛丽·张说，第一代自己不会发光的电子阅读器产品，或许还是睡前阅读一个不错的选择。但那些“背光”产品，最好还是在早上喝咖啡时看。