Why Quality Sleep Matters — and What to Do When You’re Not Getting It

The Beauty of Sleep

There are plenty of good reasons to turn out the lights and climb into bed at a reasonable hour. These are just a few of them.

1) Sleep detoxes the brain.

There’s a reason you feel so refreshed when you get a good night’s sleep — and so groggy when you don’t. When you’re exhausted and it feels like the gears of your brain are clogged, it’s because, in a sense, they are.

During the day, waste products accumulate in the brain. These are natural byproducts of our waking brainpower. When we’re asleep at night, the brain’s glymphatic system gets to work flushing away the day’s waste products. When we don’t sleep (or don’t sleep enough), the byproducts collect and muck up the gears.

“It’s sort of like having a party and leaving a mess in the dining room,” says integrative physician Frank Lipman, MD. He notes that consecutive nights of too little sleep compound the situation. “Then, say, the next day you have another party and don’t clean. The mess just builds up until it’s cleaned. The same thing happens in the brain, which is cleaned by sleeping.”

A “clean” brain allows us to learn, concentrate, and perform at our best. This is evidenced by a 2019 study that examined how the sleep habits of a group of MIT students influenced their performance on examinations. The amount and quality of sleep students got directly correlated with their test scores.

Interestingly, how much students slept the night before a test didn’t have much influence on their scores — what mattered most was the quality and quantity of sleep they’d gotten throughout the semester in which they learned the material. This showed that a good night’s sleep before a big day can be less important than quality sleep over time.

Surprising no one, sleep loss also reduces productivity on the job. A 2022 Gallup study found that more than $44 billion of lost productivity each year can be chalked up to unplanned absences due to sleep deprivation.

2) Sleep balances mood.

For many years, sleep problems were considered one byproduct of depression. But a series of longitudinal studies, in which researchers tracked the same individuals over time, have shown that sleep problems may actually be a causal factor in depression. This suggests more sleep may offer depression relief.

“People who have trouble with insomnia often have depression,” says Emmons. “If they can get their sleep back on track, their chances of recovering [are substantially better than] they would have been without improving their sleep.”

“People who have trouble with insomnia often have depression. If they can get their sleep back on track, their chances of recovering [are substantially better than] they would have been without improving their sleep.”

Insufficient sleep also increases anxiety, according to a study published by the American Psychological Association in 2023. Researchers showed that even short periods of sleep loss, like staying up an hour later than usual, resulted in participants experiencing fewer positive emotions, like joy and contentment, the next day.

Another important factor in emotional well-being is dreaming. Walker has described dreaming as a form of overnight therapy, helping us process and integrate difficult memories. These dreams can also help remove the “visceral, painful emotional charge that had previously been wrapped around those memories.”

To demonstrate, he suggests recalling a difficult childhood memory, such as feeling scared when you got lost at the mall and couldn’t find your parent. If the memory no longer conjures much fear and sadness, it’s because you’ve released those feelings through dreaming. “You have not forgotten the memory,” he writes. “But you have cast off the emotional charge, or at least a significant amount of it.”

3) Sleep improves creativity.

Dreaming helps boost creativity by acting as a sort of mixer for all our acquired knowledge. During dreams, the brain makes new connections and divines new meaning from the facts of our life. This is why we often wake with an ability to see things in a new light.

Walker describes this process as “informational alchemy” and cites the apocryphal tale of the ­Russian chemist Dmitri Mendeleev as an example of its power. Mendeleev, who was obsessed with bringing “an organizational logic to the known elements of the universe,” is said to have suffered through three sleepless nights in 1869 before finally sleeping soundly.

In his dreams that night, he allegedly saw how all the elements could fit together and, upon waking, immediately wrote it down. It was the framework of the periodic table of elements as we know it today.

4) Sleep sustains long-term health.

Sleep helps regulate the body’s cyclical systems, such as hormones and the immune system. If we don’t sleep enough, these systems can start to falter, potentially leading to the development of neurodegenerative illnesses and type 2 diabetes.

One way sleep loss and poor-­quality sleep appear to contribute to the development of type 2 diabetes is by disrupting hemoglobin A1C, a marker of blood-sugar control. ­Research suggests that better sleep may help people with the disease ­improve their blood-sugar markers.

Sleep apnea, which seriously reduces sleep quality, increases the risk of cardiovascular conditions, like hypertension, coronary heart disease, and stroke, most likely by fostering systemic inflammation.

Disruptions in a person’s circa­dian rhythm, such as night-shift work, increase the risk of certain cancers. And research suggests that chronic sleep deprivation contri­butes to neuroinflammation and the development of neurodegenerative diseases, including Alzheimer’s.

All good reasons to put that book down and turn out the light.

5) Sleep regulates appetite.

Getting enough quality sleep ensures that the body produces adequate amounts of the hormone leptin, the chemical messenger that promotes a feeling of fullness. It’s sometimes called “the satiety hormone.”

When sleep is in short supply, leptin levels drop, making it harder to feel full. At the same time, levels of the hunger-promoting hormone ghrelin go up, making us likely to eat more than we need.

This isn’t the only reason those extra pancakes always sound so good after a late night — or why we usually crave pancakes but not a spinach omelet when we’re tired. A study from Northwestern University showed sleep deprivation distorts our sense of smell, which scrambles the brain’s messages to the body about how much energy we really need. Researchers suspect this confusion helps make energy-dense foods such as sweets and processed carbohydrates even more irresistible.

(Sleep significantly influences metabolism, appetite, and weight management. Learn more at “How Does Sleep Influence Weight Gain?“)

6) Sleep supports immune function.

Sleep quantity and quality even influence how likely we are to catch a cold. A study published in the Archives of Internal Medicine found that people who averaged less than seven hours of sleep per night before being exposed to a cold virus were almost three times more likely to get sick than participants who slept an average of eight hours or more.