睡得不够，狂饮咖啡也木有用

A new study found that after restricting sleep to 5 hours per night, caffeine use no longer improved alertness or performance after three nights.

一项新近研究表明，如果每天只睡5小时，那么3天后，咖啡因对于提神醒脑及工作绩效完全没有帮助。

Results show that relative to placebo, caffeine significantly improved Psychomotor Vigilance Task (PVT) performance during the first 2 days, but not the last 3 days of sleep restriction.

研究结果显示，与安慰剂相比，咖啡因在前两天能够显著提高精神运动警觉性作业(PVT)，而从第三天起便失效了。

"We were particularly surprised that the performance advantage conferred by two daily 200 mg doses of caffeine was lost after three nights of sleep restriction," said lead author Tracy Jill Doty, PhD, research scientist at Walter Reed Army Institute of Research. "These results are important, because caffeine is a stimulant widely used to counteract performance decline following periods of restricted sleep. The data from this study suggests that the same effective daily dose of caffeine is not sufficient to prevent performance decline over multiple days of restricted sleep."

该研究的第一作者、来自沃尔特里德陆军研究院的Tracy Jill Doty博士表示：“在持续3天睡眠不足后，每日200毫克咖啡因摄入量带来的绩效帮助作用便消失了。我们对于这一结果感到非常惊讶。咖啡因被广泛地用作睡眠不足后提神醒脑的神器，而本研究的结果表明，连续睡眠不足几天后，咖啡因日常摄入量所带来的奇效便不复存在。”

The research abstract was published recently in an online supplement of the journal Sleep and will be presented Monday, June 13 and Tuesday, June 14, in Denver at SLEEP 2016, the 30th Anniversary Meeting of the Associated Professional Sleep Societies LLC (APSS).

该研究的摘要近日发表于Sleep，在本月13、14日于美国丹佛召开的第30届联合专业睡眠学会(APSS)年会上，研究者对该研究进行了报告展示。

The study group consisted of 48 healthy individuals who participated in a double blind, placebo-controlled study. Sleep was restricted to five hours of time in bed for a total of five days. Participants were administered either 200 mg of caffeine or a placebo twice daily. A cognitive task battery was administered hourly during the wake periods and included a 10-minute PVT, Profile of Mood States (POMS), and the Stanford Sleepiness Scale (SSS). A modified Maintenance of Wakefulness Test (mMWT) was administered six times per day.

研究团队征募了48名健康的参与者，参加了一项双盲、安慰剂对照的实验。研究者对每名参与者的睡眠时间进行控制：参与者首先确保连续5天10小时的充足睡眠，随后连续5天内每天只能保证5小时的睡眠，最后3天内参与者每天拥有8小时睡眠时间。参与者被指定每日分配得到200毫克咖啡因，或者安慰剂。参与者还需要完成认知任务测验，包括10分钟精神运动警觉性作业(PVT)、情绪状态量表(POMS)与斯坦福睡眠量表(SSS)，另外，每名参与者每6小时需进行1次改进的清醒度维持测试(mMWT)。