Getting 7 to 8 hours of sleep each night — don’t settle for just 6 hours
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.
No cost at all. You simply need to set aside 1–2 extra hou…
In a randomized controlled trial, 48 healthy adults aged 21–38 were asked to get just 6 hours of sleep per nig…
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 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).
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
Open source linkThe 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.