This article from the US Quartz site covers all the bases – here are the bones of it …
For something that we spend a third of our lives doing (if we’re lucky), sleep is something that we know relatively little about.
As anyone who has lain awake at night contemplating the complexities of the universe will confirm, sleep is a slippery beast. It involves a complex web of biological and neurological processes, all of which can be thrown off by something as simple as a partner’s nasal trumpeting or a coffee too late in the day.
There are so many misconceptions about sleep: that you can catch-up an the weekend for lost hours, get by on four hours a night, that a brandy night-cap helps, or that cheese last thing gives you nightmares.
To set the record straight, Quartz spoke to one of the world’s most-talked-about sleep scientists, Daniel Gartenberg of Penn State.
Some topics we cover:
- why 8.5 hours of sleep is the new eight hours
- the genes that dictate if you’re a morning person or a night owl
- why you should take a nap instead of meditating
- how sleep deprivation can be a tool to fight depression
- why sleep should be the new worker’s rights
- and tips on how to get a better night’s rest (hint: it’s not your Fitbit)
This interview has been lightly condensed and edited for clarity.
Quartz: Why do we need sleep?
Daniel Gartenberg: Every organism on the planet sleeps in some fashion, to some degree—even the basic fruit fly. What makes sleep so essential for our wellbeing comes down to three main things: to save our energy, to help our cells recover, and to help us process and understand our environment.
This third one is what I study – the synaptic homeostasis hypothesis. This is the idea that during the day, we make all these connections with the world around us. It used to be like, “Don’t go over there—the lions live there now.” Now it’s like, “What did Barbara say to me in the office?” These excitatory connections we make during the day result in the neurons in our brains getting overall higher activation. Then during the nighttime when we sleep, we have a downregulating process where the things that didn’t really matter to your survival sink to the bottom, and the things that are most relevant to your survival rise to the top. What deep sleep does is all the neural processing, and what REM sleep [rapid-eye-movement sleep] and light sleep do is basically integrate that into your long-term personality and understanding of the world.
What other differences are there between deep sleep and REM sleep?
A lot of people don’t understand that these are two very, very different processes. A lot of people probably learned from basic psych in high school that you have these sleep stages: light sleep > deep sleep > light sleep > REM, and repeat. As you sleep more, you get less and less deep sleep, and also if you sleep-deprive yourself, you get more deep sleep.
During deep sleep, you get these long-burst brainwaves, called delta waves, but during REM, your brainwaves are actually functioning very similarly to waking life. Your body is also paralyzed during REM—it’s a very noticeable physiological difference. You also lose thermo-regulation, meaning if it’s hot in your environment, your body gets hot, kind of like you’re a chameleon.
Your whole thing is that deep sleep is more important than REM sleep. Why?
It’s an ongoing debate in the literature—really, it’s both. Deep sleep is really important, but REM sleep is also important. We know that the human growth hormone, cell-recovery things, and the ability to process new information are associated with deep sleep. REM sleep is basically the processing of information.
Asking for the workaholics in the room: Do we really need that much sleep?
A professor I collaborate with at Penn State named Orfeu Buxton says that 8.5 hours of sleep is the new eight hours. In order to get a healthy eight hours of sleep, which is the amount that many people need, you need to be in bed for 8.5 hours. The standard in the literature is that healthy sleepers spend more than 90% of the time in bed asleep, so if you’re in bed for eight hours, a healthy sleeper might actually sleep for only about 7.2 hours.
8.5 hours of sleep is the new eight hours. That being said, some people are short sleepers: You can do a test to find out if you have genetic makeup that makes you a short sleeper. That’s rare, though, so by and large, people are not getting enough sleep. Getting half an hour less than you need really adds up over a week.
To see how much sleep you really need, my professor suggests that when you go on vacation, try to stick to your normal bedtime and then see what time you wake up. With no stressors or time to get up, you’ll just fall into a natural pattern, and that’s probably how much sleep you actually need.
I normally get around six to seven hours of sleep a night and feel fine. But is that just because how I feel has become my normal operating mode, and I could really be functioning at a higher level?
Let’s talk about circadian rhythms. What are they, and why are they responsible for that mid-afternoon slump?
We evolved from bacteria in the ocean that could differentiate sunlight from darkness—that’s what ended up forming the human eye. That means every organism is responsive to a circadian rhythm that’s largely dictated by sunlight. The photo receptors in our eyes pick up on sunlight, which controls the release of melatonin and all these other neurotransmitters that dictate your energy levels throughout the day.
You have a peak moment of awakeness during the morning. After lunch you usually have a glucose spike, especially if you have a big heavy lunch, like a cheeseburger. That glucose spike combined with a circadian dip gives you a period of fatigue between around 2 and 4pm. You’ll then have another spike in alertness right before dinner, and then you’ll start getting tired again closer to bedtime. That’s your 24-hour circadian rhythm, basically.
If you’re still awake, catch up on the rest of the story here:
Why eight hours a night isn’t enough, according to a leading sleep scientist