How many hours did you sleep last night? What about the night before that?
In February, an American Psychological Association survey revealed 67 percent of respondents said they were getting more sleep or less sleep than desired. A study released in June found poor sleep during the pandemic was associated with anxiety, stress, and depression.
Even before the pandemic, the people in the U.S. were struggling with sleep: A 2016 study from The CDC found that one in three people said they were sleep-deprived.
That’s not great. Despite being a poorly understood scientific phenomenon, studies consistently demonstrate how sleep is critical for health. In this article, two sleep experts discuss:
- The three signs of sleep deprivation
- Four tips for sleeping better
- Why you’re still tired even if you’re getting seven hours — and more
What is the scientific reason for sleep?
Scientists aren’t 100 percent sure why.
Philippe Mourrain is an associate professor of psychiatry and behavioral sciences at Stanford University. “It’s not accurate to say we understand everything sleep is doing for us,” Mourrain tells Inverse.
Okay — so what do we know? “We know all beings do it, and we know how sleep helps us and how sleep deprivation hurts us,” Mourrain says.
Unfortunately, there are still a lot of things about asleep we understand only part of. For example, we know people aren’t going to function well if they consistently get only four hours of sleep a night, Mourrain explains. But there’s variation when it comes to how many hours a person needs and feels fine: Some do well with six, while others need eight or nine.
There are also questions about the amount of sleep different species of animals need, Mourrain says. “We know that some species need three hours and some need 11,” he explains. “It’s incredibly variable and we don’t know for sure why that is.”
There’s also more to learn about how sleep (and sleep deprivation) affects us at the cellular level, Mourrain says.
“For decades we’ve been focused on how sleep affects our mental function, but we know it affects all species — not just humans — at the cellular level, and there is more to learn there.”
Why is it important to sleep?
Scientists are certain we need sleep to survive.
“[During sleep] the body restores energy, the muscles and cells in your body repair and grow, the information you learned from the day gets processed, and it gets stored from short term memory to long term memory,” Roban explains.
“It's not just about learning and memory, it's about you being fresh.”
Sleep also helps with our mental sharpness, not just memory.
“Say, tomorrow, I give you a math problem about which you know nothing,” Roban says. If you have a good night's sleep the night before, “you can think logically and rationally about the problem and can give a decent answer.”
“But if I prevent you from sleeping overnight, you're not going to be able to answer even very simple questions,” she adds. “It's not just about learning and memory, it's about you being fresh.”
In addition to synaptic reinforcement (the consolidation of memories), sleep is important for “synaptic pruning,” Mourain explains. Anytime we see or experience something new, we create more synaptic branches in our brain. But not everything we notice or experience in a day is something we need to integrate into our long-term memory. To help our minds be more efficient, our brains “prune” some of those branches. This happens when we sleep.
Sleep also helps regulate leptin and ghrelin, the hormones that control hunger, as well as glucose and cortisol. When we sleep, “the immune system gets stronger, and heart health gets stronger,” Roban says.
What are the signs of sleep deprivation?
According to the Centers for Disease Control, most adults need between 7 and 9 hours of sleep a night. Adults need at least 7 hours each night to promote optimal health and well-being. Some adults will need a bit more (7-9 hours per night is the healthy range). Sleep deprivation occurs when an adult gets fewer than 7 hours.
Three major components of health are affected when we are sleep deprived, Roban and Mourrain say:
3. Physical health
There are a few reasons our physical health suffers when we are sleep-deprived. The first, and most obvious, is that we don’t feel like exercising — one of the best things we can do for our physical health, and one of the best ways of decreasing stress. Higher stress can make it even harder to sleep, and the whole thing can become a vicious cycle.
Additionally, our immune system stuffers, making us more susceptible to illness.
It’s also likely that sleep deprivation negatively affects neurons, Mourrain adds: “If you have a lifetime of sleep deprivation, we think that could be a problem for neuron survival.”
Unlike skin cells, and most of the other cells in our body, neurons don’t regenerate. “If they’re exposed to irradiation and oxidative stress on a daily basis, those neurons aren’t able to repair and we think they could become fragile,” he says.
2. Emotional health
Emotional health also suffers when we’re sleep-deprived. “There’s an increased risk of mood disorders such as anxiety and depression, and exacerbation of existing mood disorders,” Roban says.
1. Behavioral health
These are likely the effects you’re most familiar with after a few nights of poor sleep and can manifest as “decreased memory, attention, productivity, efficiency, focus, problem-solving, socialization, school and work performance,” Roban says.
Why am I still tired if I get enough sleep?
If you’re getting enough sleep, but you’re still tired, a few things could be happening.
For example, you might not be getting the most quality sleep. The quality of our “awake time” directly affects the quality of our sleep, Mourrain says. Too little exercise, stress, and or even an uncomfortable room temperature can negatively influence the experience.
It’s also possible there might be something else going on: Sleep disorders are quite common and can be underdiagnosed. Insomnia is the most common sleep disorder; the American Sleep Association reports that 30 percent of adults experience short-term insomnia and 10 percent experience chronic insomnia.
Roban describes chronic insomnia as when “a person has trouble falling asleep and/or staying asleep for at least three nights per week over at least three months, and experiences excessive daytime cognitive and/or behavioral impairments from this sleep problem.”
If that’s you, it’s worth letting your doctor know and discussing treatment options.
What will help me sleep better?
First, forget about most of those sleep gadgets. “A lot of people have gadgets to improve or monitor their sleep. In my opinion, a lot of those gadgets are bullshit,” Mourrain says.
Instead, he says active, pleasant days — those with more physical activity and less stress — are the best way to cultivate better sleep.
Meanwhile, Roban recommends:
- Following a constant sleep schedule (going to bed and waking up at approximately the same time each day)
- Having a “brief and consistent sleep routine” — yoga stretches, reading a non-digital book, or even listening to relaxing music
- Avoiding screens before bed — if you absolutely have to use a screen, wear blue-light-blocking glasses
Mourrain admits that some of these suggestions are easier said than done: “It's not easy. Trust me, I am not a good sleeper and I'm a neurobiologist of sleep.” But given all the health benefits, we should all at least try.