How Did You Sleep Last Night? Understanding the Fascinating Science of Sleep

As we all manage our busy lives and schedules, it’s interesting to stop and think that most people will spend about a third of their life asleep. So why do we sleep? What purpose does it serve? It turns out that the science here is anything but a snooze. Dr. Matt Walker, Professor of Neuroscience at UC Berkeley, joined us for an eye-opening look at sleep and how we can harness the power of sleep to enhance our learning, productivity, mood and energy levels. He also explained how sleep impacts health, aging and lifespan, offering practical insights into its broader effects on well-being.

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Summary

What did we learn? Here are the top takeaways from How Did You Sleep Last Night? Understanding the Fascinating Science of Sleep:

There are four components to a good night’s sleep. Just as a good diet has three macronutrients – fat, protein and carbs – a good night’s sleep has important components as well, Dr. Walker said. They are:

• Quantity: Most people need seven to nine hours of sleep, he said.
• Quality: Ideally, you’ll be asleep at least 85% of the time you’re in bed.
• Regularity: Going to bed and waking up around the same time every day.
• Timing: This means sleeping in accordance with your natural tendency as a morning person, an evening person or somewhere in between, he said.

One study of over 60,000 people found that those with the most regular sleep patterns had the lowest risk of mortality from all causes, and specifically from cancer and cardiovascular disease, he said, adding that scientists found regularity to be the most important factor.

Knowing whether you’re a night owl or an early bird can help you take steps to enhance your sleep quality. There are over 20 genes that determine chronotype, which is a person’s natural inclination regarding the times of day when they prefer to sleep or when they are most alert or energetic. You don’t need a genetic test to find out your type. The Morningness-Eveningness Questionnaire (MEQ) can be found online and can determine your sleep timing fairly accurately, Dr. Walker said. “Chronotype is very difficult to change, and you can’t train yourself out of it,” he said, adding that those who sleep in harmony with their chronotype have a higher quantity and better quality of sleep. Society tends to be geared toward morning people, and night owls who try to fit that pattern may find they go to bed earlier than they’d prefer but end up lying in bed for an hour or more unable to sleep, he said, adding that it may look like sleep onset insomnia, but it’s not. His advice: Embrace your chronotype and adjust your sleep schedule accordingly.

Sleep plays a key role in learning. “Sleep is incredibly powerful for learning and memory, and it’s useful in at least three different ways,” Dr. Walker said. First, you need sleep before learning to prepare the memory structures in the brain to make them “like a dry sponge ready to soak up new information.” Then you need sleep after learning “to effectively hit the save button on those new memories so you won’t forget,” he said: “Sleep after learning future-proofs that information within the brain, solidifies it into the neural architecture of the brain and locks it right in.” Finally, sleep doesn’t just strengthen individual memories but also cross-links new memories, he said, adding, “You wake up the next day with a revised, mind-wide web of associations.” This, he said, is why those grappling with a difficult problem are often told to “sleep on it.”

Dreams offer “emotional first aid,” Walker said. Sleep, and particularly dream sleep, or rapid eye movement (REM) sleep, acts as a “nocturnal soothing balm by taking difficult or painful experiences from the day and smoothing the rough edges off so you feel better about them the next day,” he said. Because the brain’s emotional and memory centers get very active during REM sleep and the chemical that is essentially the brain’s adrenaline gets turned off, the brain can reprocess difficult memories in a “safe neurochemical environment,” he said, adding that this allows you to “divorce the emotion from the memory and essentially get over those events.”

It’s a myth that we need less sleep as we age. “Older adults need just as much sleep,” Dr. Walker said, adding that the misconception arose because sleep worsens with age due to changes in the brain’s ability to generate the needed sleep. This is important because just as your body has the lymphatic system for cleansing, the brain has the glymphatic system, and it switches on only during deep sleep, he said. “It’s a power cleanser for the brain,” he said. The system washes away two types of metabolic detritus that can lead to Alzheimer’s disease, which explains why insufficient sleep across the lifespan has been tied to an increased risk of Alzheimer’s later in life, he explained. The hope is that sleep research will lead to preventive therapies using technologies to boost deep sleep starting in middle age.

You probably need more sleep than you think you do. There are “genetic short sleepers” who, due to two different genes, can get by with just a little over six hours of sleep with no negative effects on the body or brain, Dr. Walker said, but it’s extremely rare. “You’re much more likely to be struck by lightning in your lifetime than you are to be one of these genetic short sleepers,” he said. Some people incorrectly think they can get by on little sleep, likely due to the human inability to gauge the effects of insufficient sleep on the body and brain, he said. One analogy: hypertension. “No one can really sense: ‘My blood pressure is really high now, it must be at least 160 over 100,’” he said, adding that insufficient sleep is similar.

An evening wind-down routine can significantly improve sleep, Walker said. “Sleep is not like a light switch,” he explained. “It’s much more like landing a plane in that it takes time to come down.” So try this experiment: Add a to-bed alarm to your phone one hour before bedtime, he suggested. At that time, turn down half, if not all, the lights in your home. “You will be surprised at how sleepy that darkness makes you feel,” he said. After one week, go back to leaving all the lights on until bedtime for another week, then ask yourself if the lights-down week was better and if the lights-on week was worse for your sleep, he said. “That’s what we call a negative-positive-negative experiment,” he said, adding that it’s a good way to see if a routine change works.

These four mind-calming tricks can head off insomnia. Most people who have insomnia, absent a medical condition, toss and turn because they can’t clear their mind, Dr. Walker said. “Everything feels much worse in the darkness of night than it does in the light of day,” he said. To fall asleep faster, he suggests, use any of these three techniques: meditation, box breathing or a body scan. A fourth option is to take yourself on a mental walk in extremely vivid detail, he said. “Let’s say I’m walking the dog. I’ll take the blue leash out of the drawer and clip it on the dog with my right hand and then open the door,” he said, noting that all these actions get the mind off itself. He added, “When you use these techniques, the next thing you typically remember is your alarm going off in the morning.”

Speaker

Dr. Matt Walker
Professor of Neuroscience, UC Berkeley 

Host

Joan Woodward
President, Travelers Institute; Executive Vice President, Public Policy, Travelers