Science 101

What Is Sleep Health?

About 35 percent of Americans rate their sleep quality as “poor” or “only fair.” Not good. Here’s how to change that.


Defining healthy sleep seems simple enough, but a quick Google is all you need to show that even researchers haven’t nailed it down. Search the term on PubMed and you’ll get over 50,000 results; Google Scholar spits out more than 3 million. Click through the studies and you’ll see that some focus on sleep duration, others on awakenings, or sleep disorders. 

Truth is, healthy sleep involves all of those aspects. “Asking what makes sleep healthy is a lot like saying ‘What’s a healthy diet?’” said Michael Grandner, Ph.D., director of the Sleep and Health Research Program and an assistant professor in the Department of Psychiatry at the University of Arizona College of Medicine in Tucson. “It’s a combination of factors.” To simplify it, he breaks it down into these three core dimensions:


Adults should get at least seven hours of slumber each night, according to the Centers for Disease Control and Prevention (CDC),  Only 35 percent of American adults hit that benchmark (we’re not alone; globally only a handful of people get enough z’s).

But Grandner says not to get too hung up on that number. “Seven hours is recommended for an otherwise healthy adult, but it’s not a hard and fast rule,” he explains, and he should know, considering he was on one of the panels that helped the CDC develop their guidelines. “But if you’re unhealthy, or an adolescent, you may need more. Older adults may need less.” There are no guidelines for an upper limit but studies have shown that people who sleep more than nine hours a night don’t live as long, although researchers don’t know why this is, said Grandner.

Another reason not to become fixated on clocking a solid seven hours? “Processes like metabolism, brain function, injury recovery, and weight management might require different amounts of sleep in different people.” You may only need six and a half hours of sleep, while your partner or friend might need slightly more than seven. 

However, the time of day—technically, night— you sleep is extremely important. This is your body’s circadian rhythm, or clock, the 24-hour pattern that most organisms follow. Staying up late can interfere with sleep and sleeping in can throw off your rhythms for the day. Shift work is also problematic because daytime sleep isn’t as recuperative as nighttime sleep, said Grandner.



One way to think about sleep quality is sleep architecture, or the way your z’s are distributed throughout the night. When you drift off, you don’t just drop into a state of suspended animation. Your brain cycles through various levels of activity several times a night.

Stage 1 Non-REM Sleep: During the first few minutes of sleep, your breathing, heartbeat, and eye movements slow down. Your brain waves start to slow into alpha and theta waves.

Stage 2 Non-REM Sleep: Your heartbeat and breathing slows further, and your muscles relax. Your brain starts to produce a slower wave frequency known as sleep spindles. 

Stage 3 Non-REM Sleep: This is the deep sleep you need to feel fresh in the morning. Your heartbeat and breathing are at their slowest pace, your muscles are totally relaxed, and your brain produces delta waves. This is when the body repairs muscles and tissues, stimulates growth and development, boosts immune function, and builds up energy for the next day.

Rapid Eye Movement (REM) Sleep: You generally enter REM sleep about 90 minutes after you fall asleep. The average person has five to six REM cycles each night, with each REM stage lasting up to an hour. During this stage, your brain is more active—this is when you dream. Your heart rate, breathing and blood pressure increase, and your eyes move in different directions (hence the name!). During REM sleep, your brain processes information and stores what it wants to keep in long-term memory.

Understanding these stages is an interesting intellectual exercise but has little bearing in the real world, said Grandner. What’s more relevant is sleep continuity, or the timeline of your slumber. Healthy sleepers should be able to fall asleep within 20-30 minutes of going to bed, rise when they intend to, and not wake for long periods during the night. Most people rouse for a few seconds between sleep cycles when their arousal threshold is low, but they’re so short they don’t remember them in the morning.

When you drift off, you don’t just drop into a state of suspended animation. Your brain cycles through various levels of activity several times a night.

If it takes you a long time to fall asleep, you wake up several times during the night for significant periods of time, your eyes pop open before you want them to in the morning, or you don’t feel refreshed in the am (one in five of us don’t, according to the National Sleep Foundation), then you could have a bigger problem.

By the way, it’s best not to rely too heavily on trackers to give you information on sleep quality. Some are more accurate than others, noted Grandner. The best ones are about 95 percent accurate, but some are only about 70 percent on the mark. “Plus, we don’t really know how much deep sleep each person needs on a nightly basis, so the data may not be that relevant.”

When Should You See a Doctor?

If you’re not hitting the above criteria or if you struggle to stay awake during the day or you zonk out before your head hits the pillow, it’s probably worth calling your doctor, said Grandner. A sleep study (where a doctor can measure your brain waves and more while you sleep) may show that you have a sleep disorder, or that you’ve just developed bad but fixable habits.

If you do have a sleep disorder, it may be treated. A form of cognitive behavioral therapy called CBTI is a successful remedy.

Researchers are also developing new technologies to help people sleep longer and better, said Grandner. Instead of wearables like sleep trackers, you might have a “nearable” such as an infrared sensor near your bed that tracks your sleep. This device could talk to other smart home gadgets to make your environment more sleep-friendly by say, dimming the lights or lowering the room temperature.

“We’re just at the cusp of this technology,” said Grandner, but within 10 years, this futuristic scenario could be reality. In the meantime, getting enough of the right quality z’s, at the right time is your surest ticket to healthy sleep.

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