We know the feeling: you roll over to check your phone. It's two minutes before your alarm is supposed to go off, and you haven't gotten that quality sleep you wished for before your head hit the pillow. Wondering how you can sleep more deeply? Us, too. No matter what, it seems like we could all do better in the shut-eye department. So we recruited the help of Rebecca Robbins, PhD, sleep researcher at NYU Langone Health, and board-certified sleep specialist Gary Zammit, PhD, executive director at Sleep Disorders Institute, for answers.
What Is Deep Sleep?
Dr. Zammit described four stages of the sleep cycle: N1, N2, N3, and rapid eye movement (REM). Deep sleep occurs in N3, also known as "slow-wave sleep," according to Dr. Zammit, and in REM. Dr. Robbins said that it's during these deeper stages that our heart rate slows and body temperature drops.
You can tell how deeply someone is sleeping by how hard it is to get the person to wake up. The further along in their sleep cycle they are, the louder the noise needs to be for them to react. "If you awaken someone from stage one sleep, very often they will tell you that they weren't sleeping," Dr. Zammit said. It's more difficult to wake someone out of N3 and REM sleep. (Note: interestingly enough, if it's a meaningful stimulus like a baby crying or someone calling their name, they wake up earlier even in deep sleep, he said.)
Why Deep Sleep Is Important
"Deep sleep is critical, but so too are the other stages of sleep," Dr. Robbins said. "It is actually this rhythmic process, experienced in totality during the recommended seven to eight hours for adults, that allows us to wake up refreshed." Experiencing each stage of sleep at night is also vital for "mood, alertness, general health, well-being, and longevity," she said, explaining that someone can normally tell if they got sufficient deep sleep if they slept for a sufficient period of time and wake up refreshed.
Dr. Zammit agreed but said we don't know exactly why all of the different stages are important. "We have ideas, but there's still a lot left to be learned," he noted, adding that most healthy sleepers experience a full sleep cycle in about 90 minutes at least four or five times per night. The REM period gets a little bit longer with each cycle. This is why clocking in the recommended hours of rest is essential. Cycling through all of the sleep stages a handful of times and getting those longer periods of REM later in the night is what enables us to feel good in the morning and function well, he said.
Of course, the amount of sleep that you need might differ from the person next to you. But if you, for example, are someone who needs nine hours of sleep every night and you're only getting seven, "no matter what you're getting, even if you're getting some deep sleep in there, you're not going to be at your peak," Dr. Zammit further explained.
Tips For Getting Deeper Sleep (aka, Better Sleep)
When you're asking how to sleep more deeply, what you're really asking is how to get better sleep — since, as both doctors explained, you'll experience deep sleep, but going through a full sleep cycle with all of the stages multiple times is what makes you well-rested. "If you feel washed out when you wake up, if you're tired, fatigued, and especially if you're sleepy during the day, it may be that you're just not getting enough sleep for you," Dr. Zammit said. Here are ways both he and Dr. Robbins said you can work on that:
- Exercise: Working out releases endorphins, "mood elevators, which can dampen stress and improve sleep onset and quality," Dr. Robbins said.
- Limit caffeine: Both doctors said that you should avoid caffeine after the morning hours because it can interfere with sleep even if it's consumed long before you go to bed.
- Limit alcohol: While alcohol has sedative properties, consuming too much before bed could make you have a restless sleep, Dr. Zammit said. (Read more about that here.)
- Stick to a routine: Try to go to sleep at the same time every night and wake up at the same time every morning.
- Avoid certain foods: If you're prone to acid reflux, try to avoid spicy and acidic foods before bed.
- Adjust your sleep environment: Sleep in a cool enough room (between 65 and 68 degrees) with as little light and noise as possible. Also make sure that your mattress and pillows are cool and comfortable.
- Get the recommended amount of sleep: On average, seven to eight hours of sleep per night is what's recommended for most adults.
A Note on Sleep Aids
Dr. Zammit noted that if you're experiencing difficulty falling asleep, you can try over-the-counter sleep aids (I tested out Som Sleep last month), though it's always a good idea to speak to your doctor first. And, for people who have more persistent problems that might be classified as a sleep disorder — sleep apnea, for example — you should definitely talk to a medical professional. That way, they can do a proper assessment for a diagnosis and any prescriptions you might need.