The A to Zzz on sleep

We spend around a third of our lives sleeping. And yet, sleep remains a mystery — and for many, a struggle. According to the Centers for Disease Control and Prevention, over one-third of adults in the U.S. report not getting enough sleep.

To help us sleep better, appreciate the wonders of sleep and answer some of our most pressing questions, four experts from Arizona State University are sharing tips and insights from their snooze-related research.

How sleep works

What is sleep?

When you’re asleep, you’re not as aware of your environment, your body’s movement is minimal and — importantly — this state is rapidly reversible, unlike hibernation or a coma. But that’s just what we can observe from the outside.

“It's a whole different set of rules in your brain that occurs when you're asleep versus when you're awake. Some areas of your brain that are not very active when you're awake light up when you're asleep, and vice versa,” says Megan Petrov, an associate professor in ASU’s Edson College of Nursing and Health Innovation.

Your body has a set of daily cycles, which scientists call circadian rhythms. One of the best-known circadian rhythms is the sleep-wake cycle, which affects when your body is sleepy or alert throughout the day. As natural light dims, your brain sends a signal to make the hormone melatonin, which makes you sleepy. This is why exposure to natural light is so important for sleep.

“The circadian system’s natural pattern is more like 24 and a half hours long instead of 24,” says Shawn Youngstedt, a professor in Edson College. “If you lived in a cave for a couple of months with no light to signal your brain, your circadian rhythm would delay a little bit every day.”

What are the stages of the sleep cycle?

Your body goes through four stages of sleep during the night, and these stages repeat in cycles. In stage 1, your body winds down and goes to sleep. Stage 2 brings a lighter sleep. In stage 3, your heartrate, breathing and brain waves are at their slowest. Rapid eye movement (REM) sleep is typically when you will dream. Graphic by Shireen Dooling

Why do we dream, walk and talk in our sleep?

Scientists have many ideas about why we dream. One popular theory is that it’s the result of our brain sorting through all the information we learned that day and filing it away, Petrov says.

“We know that by dreaming and even by recalling our dreams, we seem to learn better,” she says. “This is likely because of memories reactivating and consolidating while we dream.”

Sleepwalking is a sleep disorder, and it appears to run in families. It happens during the non-REM, deeper stages of sleep. When people sleepwalk, they may even do routine tasks, like pouring a bowl of cereal, that they often do when awake.

Sleep talking is a common behavior that some people just do more than others, Petrov says. It’s generally considered to be normal.

Why sleep matters

What factors impact your sleep?

The pandemic has amplified conversations about how health is unequally distributed across society — but did you know that sleep health follows similar patterns?

“Quality of sleep is distributed in a manner that reflects broader social inequality,” says Connor Sheehan, an assistant professor in the T. Denny Sanford School of Social and Family Dynamics. “People with more social advantage, wealthier people, higher educated people, white people — they generally sleep better than those with fewer socioeconomic resources and people of color.”

A recent study co-authored by Sheehan revealed that your spouse’s education can also play a role in your sleep, with those married to a highly educated spouse sleeping better.

If we wanted to see a more equitable distribution of sleep, I believe that we would need to have a more equitable society in everything." 

— ASU Assistant Professor Connor Sheehan

Gender also affects sleep quality. In another study that looked at the sleep health of over 1 million people from the U.S., the U.K. and the Netherlands, Sheehan found that women sleep worse than men across all three countries.

“If we wanted to see a more equitable distribution of sleep, I believe that we would need to have a more equitable society in everything,” Sheehan says.

Finally, your age impacts your sleep because sleep patterns change over your lifetime. Generally, the younger you are, the more you sleep. Newborns get up to 17 hours of sleep, while older adults may get closer to seven hours.

The biological clocks of older adults shift backwards a bit, causing them to wake up and go to bed earlier. Older adults also tend to get less stage 3 and 4 sleep, which makes their sleep feel less deep and restorative.

“You sleep worse as you get older, and that’s important because conditions that are strongly linked to sleep — like heart disease or Alzheimer's — are also a higher risk when you're older,” adds Sheehan.

How does sleep affect mental health?

Sleep and stress are closely tied together. Stress can lead to worse sleep, and unhealthy sleep is in turn a risk factor for mental health conditions.

“We're anxious about various threats in our life, which causes us to be more awake during the night. That irregularity in your sleep pattern can then become more of a chronic condition and take on a life of its own beyond what the original stressor was,” Petrov says.

Sheehan agrees, noting that a poor night of sleep not only makes the following day more challenging in the short term, but in the long term is correlated with outcomes such as depression.

There’s also a relationship working in the opposite direction — mental health disorders often carry poor sleep as a side effect. This means that sleep and mental health can get caught up in a vicious cycle. However, the good news is that people can take advantage of this connection. By working to improve one area, they may see improvements in the other, also.

How does sleep affect physical health?

“Suboptimal sleep is implicated in all of the top 10 killers of Americans,” Petrov says. These leading causes of death include heart disease, infectious disease, accidents and injuries, and diabetes.

“It's one of the three pillars of health along with physical activity and nutrition, but sleep is undervalued in our society, so it often gets forgotten,” she says.

Sheehan agrees.

“Over the long term we know that not getting enough sleep is associated with higher risk of chronic conditions,” Sheehan says. “There's a lot of research coming out now that says it's a really strong predictor of cognitive decline and Alzheimer's.”

Youngstedt says that along with short sleep, long sleep — defined as over eight hours — is tied to health threats like heart disease, stroke and inflammation.

“Just like you can get too much sunlight or vitamins or water or exercise, any healthy thing can be excessive in certain amounts,” he says. The long sleep that he describes is more than just sleeping in on an occasional Saturday — it’s chronically sleeping more than you need.

Sleep disorders

Do we have a sleep disorder epidemic in the U.S.?

Sleep disorders are conditions that disturb your normal sleeping patterns. They can affect your ability to fall or stay sleep, your ability to stay awake during the day, your circadian rhythm or your behaviors while asleep.

Whether these disorders are an epidemic is controversial, says Petrov. That’s because it’s hard to get accurate data about how people slept in the past. It does seem that some groups in society sleep worse now than in prior decades, following the pattern of today’s sleep health disparities.

One clear trend she sees is more variability in our sleep today than in the past.

“There's a lot more irregularity in people's schedules. Sometimes they only allow for short sleep opportunities, then long, and they're flip-flopping between weekdays and weekends,” Petrov says.

Insomnia is the common cold of dealing with stress. So, we've definitely seen with the pandemic that insomnia symptoms have greatly increased.” 

— ASU Associate Professor Megan Petrov

Other trends in sleep disorders are tied to larger trends in health. Increased obesity, for example, has led to an increase in sleep apnea. Times of mental health challenges also have an impact.

“Insomnia is the common cold of dealing with stress. So, we've definitely seen with the pandemic that insomnia symptoms have greatly increased,” she says.

Sheehan’s research has found that Americans have self-reported getting less sleep since about 2013.

“Is there a sleep epidemic? About a third of Americans aren't getting enough sleep. A third of the population suffering from any health condition would be called an epidemic, I think,” he says. “It's troubling that it's especially concentrated among disadvantaged communities.”

Youngstedt’s research suggests that health outcomes from long sleep have potential to affect more people than short sleep, even though short sleep is more widely studied.

“There have been studies that looked at the percent of sleep-study participants who reported different amounts of sleep. In several of them, the percent of people reporting eight or more was greater than the percent of people reporting six or fewer,” Youngstedt says.

How do you find out if you have a sleep disorder?

Matthew Buman cautions that you should not get overly concerned just because a consumer device like a fitness watch or smartphone app tells you that you’re sleeping very light. Data from these devices is not always accurate, especially when it comes to measuring sleep stages. Instead, listen to your body.

“The thing to pay attention to is whether you feel like your ‘light sleep’ is actually disrupting your daytime behavior. Does it cause you to feel sleepy during the day? When you wake up in the morning, do you not feel well rested?” says Buman, a professor in the College of Health Solutions.

If you suspect you may have a sleep disorder, go see your doctor. They can help you figure out if you have an underlying medical issue that’s affecting your sleep instead. However, Petrov notes that most primary care providers are not specifically trained in sleep, so if they agree that there could be a disorder at play, they will likely refer you to a sleep medicine specialist for a diagnosis.

What else are ASU scientists researching about sleep?

Petrov, along with fellow ASU Associate Professor Corrie Whisner, is working on a study funded by the National Institutes of Health that will explore how babies’ sleep-wake cycles affect their gut microbiomes, and how this in turn affects whether they experience rapid weight gain in their first six months — considered a predictor of childhood obesity. This effort, called the ASU Snuggle Bug/Acurrucadito Study, could lead to better sleep and diet recommendations for infants, helping them grow into healthier children. Read more about this research.

Sheehan's current research is focused on how where you live influences your sleep. He is also curious to see how sleep changed in the U.S. during 2020.

“For the first time, a lot of Americans actually had more time to sleep, but at the same time, it was one of the most stressful years in a century,” he says.

Youngstedt will soon begin work on a study funded by the Department of Defense that will develop ways to help people recover from jet lag faster. He will test combinations of light exposure, melatonin and strategically timed exercise on volunteer study participants.

“Military special forces have to travel to the other side of the planet and be ready to go very quickly, with potentially dire consequences if they're not and have a resulting error in performance or reaction time,” he says.

Though the stakes may not be as high for jet-lagged civilians, the findings could help the everyday traveler as well.

How to improve your sleep

How much sleep do you really need?

The National Sleep Foundation suggests the average adult needs seven to nine hours of sleep per night. However, sleep is very individual — each person’s needs are a little different.

“The optimal way to figure out how much you need is to listen to your body and essentially not live on an alarm clock,” Buman says. “The idea is to focus on when your body is saying, ‘I’m sleepy,’ and to sleep. Then, wake up when your body wakes up.”

If the idea of quitting your morning alarm gives you a haunting vision of rushing to work two hours late in your robe and slippers, Buman has an alternative that still benefits your health.

“Pick a regular time to wake up and be very consistent with that time, not varying it more than an hour, even on the weekends,” he says. “Your body will, over time, adjust to that routine and send a more effective signal to your body in the evening for when you're sleepy. Then your body will regulate to the optimal amount of sleep.”

7 tips to help you sleep better

Researchers recommend practicing good sleep hygiene — a set of healthy habits that help you fall asleep faster, stay asleep through the night and wake up feeling more refreshed. These include:

• Be consistent. Go to sleep and wake up at the same time every day.
• Get regular exercise, whenever you can. “There has been an adage out there that people should avoid exercise before bed, but that generally is not the case,” Buman says. “Anytime you have an opportunity to exercise, it will benefit your sleep.”
• Keep your cool. Instead of bundling up with heavy blankets and warm pajamas, wear light clothing and keep your bedroom cool to help you fall asleep faster, says Buman. That’s because your lowering body temperature prompts you to fall asleep. You could also try taking a warm bath or shower before bed. This raises your temperature, forcing your body to cool itself off.
• Adopt a sleep-friendly diet. Buman suggests limiting caffeine to the morning, staying away from high-fat and sugary foods before bed, and not using alcohol to help yourself get to sleep. Alcohol may help you fall asleep, but once its sedative effect wears off, you can wake up in the middle of the night.
• Avoid screens in the evening, since most smartphones and TVs emit blue light. Blue light disrupts a hormone called melatonin which tells your body to fall asleep.  If you can’t avoid screens, you can use blue light filters that are a common feature of many smartphones or even wear glasses that block blue light.
• Expose yourself to natural light. “Getting outside is important for regulating the body clock,” says Youngstedt. “I think a lot of people don't get outside enough, especially in Arizona in the summertime.”
• Don’t worry about being perfect. As a behavioral sleep specialist, Petrov has found that, ironically, worrying about getting enough sleep can keep you awake at night. “Long ago, some of my patients had this expectation that they're supposed to get eight hours of sleep, no matter what, and if they didn't get that, they feared they would suffer some major consequences the next day,” she says. “The thought of that consequence happening is what made it hard for them to unwind from the day and actually allow themselves to fall asleep or fall back to sleep in the middle of the night.”

Can you train yourself to fall asleep faster, sleep more deeply or become a morning person?

You can use sleep hygiene strategies to help yourself get better quality sleep. However, if your trouble with falling asleep or sleeping too lightly is a persistent, disruptive problem, you should consult a doctor to see if you may have a sleep disorder.

Changing your circadian rhythms may be a bit more difficult.

“There's a relatively strong genetic component for being a night person or being a morning person,” Buman says.

However, it’s not all bad news for night owls who want to adjust their body clocks.

“The majority of individuals are not extreme night or morning people; they're sort of in the middle,” he says. “That's good news because there isn't as much of a shift that needs to occur.”

Healthy sleep habits, as well as choosing a consistent wake time, are key in helping you accomplish that shift. Loathsome as it may seem, setting your alarm every day and getting yourself out of bed will eventually teach your body its new routine.

“If you are an extreme night person, that will be very difficult, but it can be done over time, though it may take several weeks,” he says.

Should you use a sleep tracker?

“It depends on what exactly you’re trying to measure about your sleep,” Buman says.

For the average person, sleep trackers are pretty accurate at measuring how much time you spend asleep, which they do by sensing your movement. Unfortunately, sleep trackers are not as good at this if you have insomnia, a condition that makes it difficult to fall asleep. That’s because as you lie still in bed trying to fall asleep, devices will believe you are sleeping and overestimate your actual sleep time.

Sleep devices are also not very accurate at measuring sleep stages, which some apps call “light sleep” and “deep sleep.”

“Sleep stages are a much more complex series of measures. It's really about brain activity,” Buman says. “And of course, these devices don't measure brain activity; they measure movement on the wrist.”