03-003 · EVIDENCE A · LOW-RISK READING
Getting 7 to 8 hours of sleep each night — don’t settle for just 6 hours
每晚睡够 7 到 8 小时，别把 6 小时当作够用
No cost at all. You simply need to set aside 1–2 extra hours each day for sleep. Going to bed earlier requires a bit of willpower.
After two full weeks of getting only 6 hours of sleep each night, brain performance drops to a level equivalent to going two full nights without any sleep at all. The tricky part is that people don’t notice this effect themselves. Their self-rated sleepiness only rises during the first few days and then plateaus — people sleeping 6 hours report the same level of fatigue as those sleeping just 4 hours. In other words, the belief that “6 hours of sleep is enough for me” is actually a symptom of chronic sleep deprivation.
A
Move “Getting 7 to 8 hours of sleep each night — don’t settle for just 6 hours” to Future Me's calendar
The excuse
One more exception feels free because the bill arrives outside the current scene.
What feels good now
Today I keep a few minutes, a bit of persistence and avoid interrupting my default routine.
What the source says
The source summarizes the return this way: “After two full weeks of getting only 6 hours of sleep each night, brain performance drops to a level equivalent to going two full nights without any sleep at all. The tricky part is that people don’t notice this effect themselves. Their self-rated sleepiness only rises during the first few days and then plateaus — people sleeping 6 hours report the same level of fatigue as those sleeping just 4 hours. In other words, the belief that “6 hours of sleep is enough for me” is actually a symptom of chronic sleep deprivation.” Evidence grade A. The original states the population, caveats, and sources; this is not a personal forecast.
Open the original entry, check who the evidence applies to, then pick one small step that fits.
THE ENGLISH EDITION
Original recommendation and evidence
3. Getting 7 to 8 hours of sleep each night — don’t settle for just 6 hours
Cost: No cost at all. You simply need to set aside 1–2 extra hours each day for sleep. Going to bed earlier requires a bit of willpower.
In plain terms: After two full weeks of getting only 6 hours of sleep each night, brain performance drops to a level equivalent to going two full nights without any sleep at all. The tricky part is that people don’t notice this effect themselves. Their self-rated sleepiness only rises during the first few days and then plateaus — people sleeping 6 hours report the same level of fatigue as those sleeping just 4 hours. In other words, the belief that “6 hours of sleep is enough for me” is actually a symptom of chronic sleep deprivation.
Benefit: In a randomized controlled trial, 48 healthy adults aged 21–38 were asked to get just 6 hours of sleep per night for 14 consecutive days. Their cognitive performance steadily declined, eventually reaching levels comparable to those seen after two full nights of total sleep loss. Meanwhile, their self-reported sleepiness only increased at first and then remained largely unchanged. There was no difference in self-rated fatigue between the 6-hour and 4-hour sleep groups. Additionally, a meta-analysis of 70 studies found that acute sleep deprivation (lasting no more than 48 hours) leads to a moderate drop in simple attention (effect size g = -0.776) and a much smaller decline in reasoning accuracy (g = -0.125).
Evidence grade: A
Sources: Van Dongen, Maislin, Mullington & Dinges (2003). The cumulative cost of additional wakefulness. Sleep. <https://doi.org/10.1093/sleep/26.2.117>; Lim & Dinges (2010). A meta-analysis of the impact of short-term sleep deprivation on cognitive variables. Psychological Bulletin. <https://doi.org/10.1037/a0018883>
Notes: The most important takeaway is that “not feeling sleepy” is not proof that you’ve gotten enough sleep. People who regularly sleep just 6 hours simply get used to the state, but their actual performance does not improve. The results from the meta-analysis apply to staying awake for an entire night; there is only one randomized controlled trial supporting the idea that consistently getting less than 6 hours of sleep has any real negative impact.
Read the complete Chinese source and notes
3. 每晚睡够 7 到 8 小时，别把 6 小时当作够用
成本: 不花钱。每天要多留 1 到 2 小时给睡眠。早一点上床，需要一点毅力。
说人话: 连着两周每晚只睡 6 小时，脑子的表现会掉到相当于两天两夜没合眼的水平。麻烦的是自己感觉不到。自己打分的困倦头几天涨完就不再涨，睡 6 小时的人和睡 4 小时的人打分一样困。所以「我睡 6 小时够用」这句话本身就是缺觉的症状。
收益: 48 名 21 到 38 岁的健康成人，连续 14 天每晚只睡 6 小时。他们的脑力表现累计下降，掉到相当于连续 2 晚完全不睡的水平。而自己打分的困倦程度只在头几天上升，之后几乎不再增加。6 小时组和 4 小时组的自评困倦没有差别。这是把人随机分成两组做的对照试验（RCT）。另外，短时间不睡（急性睡眠剥夺，不超过 48 小时）对简单注意力走神的效果大小 g = -0.776，对推理准确率 g = -0.125。这部分是把 70 项研究合起来算的。
证据等级: A
来源: Van Dongen, Maislin, Mullington & Dinges (2003). The cumulative cost of additional wakefulness. Sleep. <https://doi.org/10.1093/sleep/26.2.117>；Lim & Dinges (2010). A meta-analysis of the impact of short-term sleep deprivation on cognitive variables. Psychological Bulletin. <https://doi.org/10.1037/a0018883>
备注: 「自己觉得不困」不是睡够了的证据。长期睡 6 小时的人只是感觉上习惯了，表现并没有跟上。汇总多项研究的那部分说的是整夜不睡。「长期少睡」只有一项随机对照试验支持。睡多久和死亡风险的关系另算，见第 2 节第 13 条（每晚睡 7 小时左右）：那边按死亡率算，7 小时那档风险最低。
YOUR PRIVATE LIST