Sleep is a commodity most of us treasure.

There’s nothing like the proverbial “good night’s sleep” to make the body feel rested and the mind refreshed, to say nothing of the pleasures of sliding under a warm comforter on a cold night and, if we are lucky, drifting off into sweet dreams.

But sleep does so much more than cure sleepiness, restore our energy and provide us with an unconscious respite from daily life. Even for people who aim to catch as few Zs as possible and declare “I’ll sleep when I’m dead,” the fact remains that sleep — like food, water and exercise — is critical to their health.

“Sleep is so important, and it is foundational in almost everything. We spend one third of our lives sleeping, and there is nothing else in our lives we spend an entire third doing,” said Nancy Stewart, D.O., assistant professor of pulmonary, critical care and sleep medicine at the University of Kansas Medical Center. Stewart noted that during sleep, the body removes toxins from the brain and spinal cord, processes and stores memories and produces proteins that enable the immune system to fight infections. “And if we don’t have good quality sleep and good duration, the body can’t do those things and function the way it’s supposed to.”

Getting sufficient and quality sleep can help people not get sick, maintain a healthy weight, reduce stress, improve heart health and lower the risk of chronic conditions such as Type 2 diabetes, high blood pressure and stroke. A lack of sleep also puts people at risk for injuries, such as those caused by drowsy driving. In 2022, the American Heart Association added sleep to its checklist of healthy behaviors for optimal heart and brain health. Aetna, one of the largest health insurers in the United States, pays its employees just over one dollar, up to $300 per year, for each night they sleep more than the recommended minimum of seven hours, as part of its
wellness program.

So, it’s safe to say that the jury is in, and the verdict on sleep is that it’s critical. But as much as scientists have learned, in many ways sleep remains a mystery.

And as Stewart notes, the field of sleep medicine is relatively new.

Wake up call

Not that people haven’t been trying to solve their sleep problems since forever. Before drinking warm milk and counting sheep were considered remedies, people used poppy seeds (opium) and a variety of other plants and herbs as well as alcohol to help them sleep. Some cultures believed bloodletting was the answer. Charles Dickens, who used to walk the streets of London when he couldn’t sleep, is reported to have slept in his bed facing north with his arms outstretched, a position he believed would both spur his creativity and ease his insomnia.

The modern era of sleep medicine didn’t begin until the 1950s when University of Chicago physiologists discovered REM (rapid eye movement) sleep after they hooked up sleeping subjects to an EEG (electroencephalogram) and recorded eye and brain activity. Before then, it had been assumed the brain was mostly dormant during sleep. The discovery of REM led to researchers discerning that sleep occurs in cycles or stages, that sleep stages are regulated by hormones such as melatonin and cortisol and that dreaming occurs during REM sleep. In the decades since, many studies have linked sleep deficiencies with obesity and heart attacks, as well as with chronic diseases such as diabetes, high blood pressure, and depression and anxiety.

In the 1970s, the first sleep clinics opened to treat disorders such as narcolepsy, which causes excessive daytime sleepiness, and sleep apnea, which is characterized by repeated episodes of breathing cessation (apnea) during sleep. It wasn’t until 1975 that insurance companies began reimbursing claims for sleep medicine because the field had been considered largely experimental. The same year saw the formation of the American Academy of Sleep Medicine (AASM), whose functions include accrediting sleep medicine facilities in the United States. By 2024, the AASM had accredited more than 2,300 sleep centers and clinics.

But despite the growing knowledge about the importance of sleep and the establishment of sleep medicine as a specialty, one in three American adults do not get the recommended minimum of seven hours of shuteye a night on a regular basis, according to the Centers for Disease Control and Prevention (CDC). Children aren’t doing any better, with one-third of kids younger than 14 and three-quarters of high school students not getting enough sleep. Moreover, the CDC estimates that 50 million to 70 million Americans have chronic sleep disorders such as sleep apnea.

Scientists don’t yet fully understand the biology of how sleep keeps so many bodily processes working properly or how to solve everyone’s sleep issues. And we don’t yet know the curative effects of sleep: if and how much improving sleep can prevent the onset of diseases or lessen their severity. At research centers across the country, including at KU Medical Center, scientists are working to find better treatments for sleep issues and to elucidate connections between sleep problems and various diseases.

Perchance to sleep

Damien Stevens, M.D., associate professor of pulmonary, critical care and sleep medicine at KU Medical Center, studies sleep issues and treats patients at the sleep clinic at The University of Kansas Health System. Uncovering the source of patients’ sleep issues is a big part of his job, and dealing with other health issues affecting sleep is par for the course in sleep medicine, he said. Anxiety, neuromuscular diseases, and heart failure, for example, all impact sleep. “Sleep is a specialty that intersects with almost every other medical specialty,” said Stevens.

For people with no other health issues, busier and more stressful lives, 24/7 media saturation and the use of smartphones and other screen technology are often cited as culprits for sleep deficits. Stevens also noted that wearable sleep-tracking devices, such as Fitbits and Garmin smartwatches, can be “a double-edged sword.” Although they help diagnose chronic conditions such as sleep apnea, using them for constant monitoring increases anxiety in some patients, which worsens sleep issues such as insomnia. “It can be very counterproductive,” Stevens said. “It’s probably one of the biggest new things in sleep medicine we didn’t deal with 10 or 20 years ago.”

Stevens believes one of the best treatment options to have emerged over the past couple of decades for people who cannot sleep is cognitive behavioral therapy for insomnia (CBT-I), sometimes in conjunction with sleep medication that, ideally, people eventually stop taking. CBT-I combines cognitive therapy with good “sleep hygiene”: Not using one’s phone or computer in bed. Not watching television in bed. Adhering to a regular sleep schedule. Keeping the bedroom cool, dark and quiet. Avoiding caffeine and alcohol before bed. Limiting naps.

Meanwhile, Stevens is studying treatment options for people with sleep apnea, which results when over-relaxed muscles block the airway. People with a high body mass index (BMI) are at higher risk for the disorder because excess fat can narrow their airways. The first-line treatment for this disorder is continuous positive airway pressure (CPAP), a device that delivers a constant stream of pressurized air through a mask that keeps the airway open and prevents breathing interruptions. CPAP devices are effective, but roughly one-third of patients struggle to tolerate wearing the apparatus, Stevens said.

In addition to researching a drug that affects the control of breathing within the brain, Stevens is the lead investigator on a multisite trial testing a tiny surgically implanted device that stimulates the hypoglossal nerve and opens the back of the throat. The devices are already considered effective for sleep apnea sufferers with a lower BMI; soon, the study will begin enrolling participants with a high BMI.

Stevens is also the lead site investigator on an ongoing multisite study called RECOVER-SLEEP about sleep disturbances related to long COVID. People with long COVID have struggled both with changes in sleep-wake patterns, such as insomnia, and with hypersomnia, which is sleeping longer than usual or feeling tired during the day even after a full night’s sleep. For the participants with hypersomnia, the study is testing two repurposed drugs that promote wakefulness.

For the participants who have poor sleep quality or insomnia, the study will test a combination of melatonin supplements, behavioral education materials and light. “The patients are prescribed bright light in the morning (lamps) to try to sync their circadian rhythm with the light to improve their symptoms,” said Diego Mazzotti, Ph.D., co-principal site investigator for the study, sleep researcher and assistant professor of medical informatics at KU Medical Center.

Get rhythm

Each person’s sleep-wake cycle — when they sleep and when they wake up — is regulated by two mechanisms. One mechanism is sleep homeostasis, sometimes called sleep drive. It refers to the desire to sleep that grows over time while we are awake.

Circadian rhythm is the other mechanism, and it’s a tad more complicated. It refers to the body’s system of internal clocks that aligns our sleep-wake pattern with the day-night cycle. There is a kind of master circadian clock in the brain, which coordinates with the other clocks we have in nearly every cell and tissue of our bodies. The master clock is composed of genes that encode proteins that activate the other clock genes, and these genes are activated at different times over day and night. Circadian rhythms help the body respond to cues from the environment, including temperature, food, physical activity and especially light. People who are blind often have trouble sleeping because they cannot detect the light.

A person’s circadian rhythm, then, is influenced both by their genetics as well as their environment. That is why it is not really possible for someone to change herself from a night person to a morning person. It is, however, important for people to try to align their sleeping as much as possible with the day-light cycle because when their eyes see sunlight, hormones that promote wakefulness are activated quickly.

“There is strong evidence that there is a genetic effect on circadian preference, so if you try to force yourself to be a morning person, when your genetics tell you that you’re an evening person, that’s just going to be bad for you,” said Mazzotti. “The goal is more to try to synchronize with the current day-night cycle so you will be more comfortable.”

Sleeping well is clearly healthier for people, but whether it can stave off or even treat specific diseases is still an open question, and one that some researchers at KU Medical Center and the University of Kansas are trying to answer.

Combating multiple sclerosis and Alzheimer’s disease

Sleep was not a topic that was covered in Katie Siengsukon’s physical therapy training program, and it wasn’t something she was attuned to after she graduated. But when she started working as an outpatient PT, she noticed that many of her patients had some kind of sleep issue. When she went back to school to earn her doctorate at KU in 2004, she decided to do her dissertation on the importance of sleep on memory consolidation and motor learning for people with neurological conditions.

“That was a narrow aspect of sleep,” said Siengsukon, Ph.D., professor of physical therapy, rehabilitation science and athletic training at KU Medical Center. “But it really opened my eyes to the importance of sleep for pretty much every system of the body — tissue healing, immune function, cognitive function, physical function.”

Siengsukon, the first physical therapist in the country to become board-certified in behavioral sleep medicine and the director of the Sleep, Health and Wellness Laboratory at KU Medical Center, said that her lab has shown that improving sleep through CBT-1 can help people who have suffered a concussion. A doctoral student in her lab did a study showing that CBT-1 improved sleep outcomes in these patients — and that it also improved their post-concussion symptoms and a biomarker that indicates the integrity of their neurons.

Her lab also has conducted three pilot studies demonstrating that CBT-1 improved not only sleep for people with multiple sclerosis (MS), but also improved their fatigue, depression and quality of life. She currently is running two larger trials on CBT-1 with this population, one of which is evaluating if CBT-1 delivered by videoconferencing is effective.

“There’s a lot of evidence that CBT-1 is an effective intervention; there just isn’t a lot of research that has been done in people with MS or other neurological conditions,” she said.

Additionally, Siengsukon is leading a trial focused on the effect of improved sleep on the development of Alzheimer’s disease in older adults. People with insomnia and daytime sleepiness are at higher risk for Alzheimer’s, and sleep impairment is common in people with the disease. A hallmark of Alzheimer’s is the accumulation in the brain of a protein known as amyloid-beta, and the new treatments for the disease that have come out in the last three years aim to clear this protein from the brain.

Siengsukon’s study is evaluating the effectiveness of CBT-1 in older adults with insomnia not only in improving sleep, but also in reducing the buildup of amyloid plaques.

“If we can show that helping people sleep better actually reduces the rate of amyloid-beta accumulation, it could potentially impact the onset of Alzheimer’s disease,” she said.

Two birds, one stone

Sleep disorders are more prevalent in people with neurodevelopmental and intellectual disabilities, noted Olivia Veatch, Ph.D., an assistant professor in the Departments of Psychiatry and Behavioral Sciences and Cell Biology and Physiology at KU Medical Center. Moreover, she said, those sleep and circadian rhythm deficits often show up before the symptoms of the neurodevelopmental disorder. This is true of autism, for example; sleep and circadian rhythm deficits present in the first year, but the disorder usually is not diagnosed until well into the second year
of life.

“One of the functions of sleep is that, during that stage of our life when our brains are developing, when we’re sleeping, there’s a lot of neural patterning going on, so synapses are being built and pruned,” Veatch said.

Veatch maintains that there are genetic factors that contribute to neurodevelopment disorders and simultaneously affect sleep. By addressing the sleep then, she reasons, you can also potentially benefit brain development. She is currently working to identify the genetic factors that are disrupted in people who have schizophrenia that also regulate sleep and wake cycles.

And she is looking at a rare genetic disorder known as Prader-Willi Syndrome. People who have Prader-Willi have learning difficulties, short stature, muscle weakness and behavior problems, including sleep disturbances. They also have an insatiable appetite that leads to early-onset obesity; the most common cause of death for people with Prader-Willi are complications related to obesity, such as diabetes and hypertension.

“Normally I’m focused on brain development and the role of sleep in that, but for this project, I’m also interested in what role sleep plays in a healthy metabolism,” said Veatch. “It’s all interconnected.”

“If we can focus on identifying those genetic mechanisms that overlap and find better ways to treat the sleep problem, then we might be able to do that during a window when it could actually improve neurodevelopmental outcomes,” she said. “There are periods of neurodevelopment that may be crucial to needing to have a good night’s sleep in order to develop
healthy brains.”

Not-so-sweet dreams

Some researchers are looking to improve health through their dreams, literally. Nancy Hamilton, Ph.D., is an associate professor in the Department of Psychology at the University of Kansas, where she directs a laboratory focused on research related to sleep, dreaming and nightmares as they relate to physical and
mental health.

One of the leading theories about dreams, Hamilton said, is that they are a place in which memory gets updated and consolidated — “filing information in the right folder,” as she put it — a process known as “dreaming to remember.”

Her lab is especially focused on the role of nightmares, defined as dreams with fearful content that also awaken the dreamer, in post-traumatic stress disorder (PTSD). Chronic nightmares are a hallmark of PTSD.

“One of the things that can be really helpful following trauma is having dreaming episodes that help you process and put together memories about the event, maybe even kind of pair them with some less dysphoric elements. When people do that, they may be able to kind of forget and move on from the trauma or the bad event. In research we call that ‘dreaming to forget,’” said Hamilton. “But if someone is having nightmares, we think they really disrupt that dreaming-to-forget process.”

When people have such chronic recurring nightmares, they can become afraid to go to sleep, which leads to insomnia, and a vicious cycle ensues.

So how do you treat nightmares? There are anti-hypertensive drugs that have some effect, but the most effective treatments, Hamilton said, are “rescripting” therapies, in which people literally write (re-script) a new ending for their nightmare.

Hamilton recalled a firefighter who was having nightmares about his tour in Vietnam and seeing the men in his platoon being killed.

“In his nightmare, he would see that event unfold over and over,” she said. “The rescription that worked for him was telling those men that he would remember them and who they were before they were killed.”

Hamilton said rescripting therapy works for about half of people who try it. She is trying to improve this by taking people’s dream narratives and using AI software to create brief videos of people’s nightmares. The ultimate goal? That the person would then be able to watch their dream with their re-scripted ending, and that this improved sleep would alleviate their PTSD.

A trajectory for better health

Stewart, meanwhile, is studying patients who have both sleep apnea and chronic obstructive pulmonary disease. COPD is the fourth leading cause of death worldwide, and sleep apnea and COPD often coexist. People with COPD often die from cardiovascular disease. “If we can help these patients from a sleep health perspective, the long-term thought is it not only improves their COPD, but it should improve their cardiovascular health and therefore, hopefully, their morbidity and mortality,” she said.

Stewart emphasized that improved sleep is helpful not just for sufferers of particular diseases such as COPD, but for everyone — including the health care teams, often sleep-deprived, that take care of people.

“If we can improve this one thing, think about the trajectory that it could have on our life and our health.”