What is Sleep Quality?

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The quality of sleep is a broad term that can be looked at from different angles. The aim of this article will be to share the most important points related to sleep quality and give an initial understanding of how getting a good night's rest can positively impact your life.

Sleep quality is not only related to the number of hours spent sleeping per night, but also to how efficiently your body is able to complete its sleep cycle. The most important parts of the sleep cycle are when your brain stays in a light slumber known as Rapid Eye Movement (REM) and when you enter deep sleep, also known as slow-wave or delta sleep.

Sometimes people wake up directly from REM sleep, which makes them feel like they didn't get enough rest after sleeping 8 hours. It is important to remember that every part of the sleep cycle has its purpose and meaning for your body's overall health, especially when it comes to muscle recovery, memory consolidation, and overall cognitive function.

To understand why getting quality sleep is important, it's useful to take a look at the different stages of sleep. The main cycles are composed of Rapid Eye Movement (REM) and slow-wave/deep sleep (SWS). The first 90 minutes of sleep are usually spent in SWS while REM makes up for about 20% of total sleep. Deep sleep is the most important stage as it is where your body recuperates and regenerates itself, releasing growth hormones that are responsible for muscle gain or fat loss. The brain will be restoring its neurotransmitter levels during this time, including serotonin which can impact moods, catecholamines that regulate.

How do you Measure Sleep Quality?

There are many different ways to measure sleep quality. The most popular metrics currently available revolve around measuring brain waves during sleep, heart rate variability (HRV), and levels of hormones such as cortisol and melatonin.

Brain waves can be measured by EEG machines that use sensors attached to your head in order to determine what stage of sleep you are in. As you go through each stage of sleep, there is a shift in the frequency and amplitude of brain waves. The most important states to measure are REM and slow-wave/delta (deep) sleep; however, it can be useful to get more information on all stages of your sleep cycle.

To get an accurate picture of how your body is sleeping, it's useful to start with a baseline by using an EEG device. HRV can be measured through various devices such as belts worn around your chest or smartwatches. Heart rate variability is a sign of how relaxed and in-tune your body is with its surroundings. If your heart rate is perfectly in sync with your environment, it proves that you are totally relaxed and ready for quality sleep.

Gathering data on hormones can be done through simple saliva or blood tests which measure the levels of melatonin (a hormone responsible for inducing sleep) and cortisol (a hormone associated with stress).

Saliva tests, such as the kind that can be done at home through a self-test kit, are easy to use and widely available. It's important to note that sleep is a necessary process for these hormones to be produced, so it's helpful to get more information on how your body is performing during your rest.

Illustration of a Dream Experiment During the REM Sleep

What is the Pittsburgh Sleep Quality Index?

The Pittsburgh Sleep Quality Index (PSQI) is a method of measuring sleep quality and patterns by evaluating 7 different components: subjective sleep quality, sleep latency (the time it takes to fall asleep), sleep duration, habitual sleep efficiency (ratio of time spent sleeping vs. time intended for sleeping), sleep disturbances, use of sleeping medication, and daytime dysfunction.

The subjective component of the test gives you a better idea of how you feel during the day and your general mood by asking questions such as “How restful was your sleep last night?” or “How would you rate your sleep quality?”

The next part of the test looks at sleep latency, which is an important predictor of how likely it is that you will develop a sleep disorder. Sleep latency is the amount of time it takes for you to fall asleep after going into your bed where you intend to rest. Next, there is the duration of sleep and efficiency which not only look at how long and how often you are sleeping (duration) but also at whether or not it's spent in an efficient manner.

Habitual sleep efficiency looks at the quality of your sleep relative to how much time you spend in bed trying to go to sleep. The PSQI also evaluates the occurrence of specific sleep disturbances, including insomnia, excessive waking after going to bed and taking more than 30 minutes to fall asleep on average every night. This test is useful to examine how your sleep patterns are affecting your overall health by looking at other measures such as heart rate variability.

What are the Sleep Quality Statistics?

The U.S. Center for Disease Control (CDC) reports sleep statistics gathered via survey every few years. The most recent results give us an idea of how common sleep disorders are. Based on the survey’s results, here are some statistics about the state of national sleep quality:

  • 35 percent of adults in the United States report sleeping less than 7 hours per night
  • Over half of American adults report experiencing daytime sleepiness at least a few times a week
  • Over 10% of adults report chronic insomnia symptoms that interfere with their daily lives

Based on these statistics, we can draw some conclusions about the state of sleep in our nation. While there is certainly progress to be made, it seems the majority of people are content with the quality of sleep they’re receiving.

At times it may feel normal to not be getting enough sleep and even expected in some work cultures, however poor sleep quality is not normal, and it’s certainly not healthy in the long run.

What are the Factors that Affect Sleep Quality?

Illustration of a Woman Sleeping on Her Side with Her Eyes Open

There are many factors that can influence how well we sleep, including age, gender, stress levels, medical conditions, environment, caffeine intake, alcohol consumption, nicotine intake, and other medications we may be taking.

  • Age – Research shows that sleep problems are more common in older adults than younger adults. The reason may be due to the fact that many older people struggle with age-related conditions or chronic pain, which makes it difficult for them to get adequate rest.
  • Gender – While men and women experience insomnia at similar rates in adulthood, women are much more likely than men to have insomnia symptoms in midlife.
  • Stress – When people are under stress it is common for them to experience many different health problems, including trouble sleeping. While this may be due to the fact that too much stress hampers your body's ability to regulate hormones and maintain mental stability, research shows there could be a genetic influence
  • Medical conditions – Many medical conditions can contribute to a person's risk for developing insomnia, including breathing problems such as chronic obstructive pulmonary disease (COPD), psychiatric conditions, and neurological disorders. Diabetes is one of the large factors that affect sleep quality.
  • Environment – Poor sleep quality may be related to external factors in the environment that interfere with sleep, such as noise or discomfort. If you live in a noisy environment, you may find it difficult to fall and stay asleep. Similarly, if you're sleeping on a poor-quality mattress, you may find yourself tossing and turning for longer in the night.
  • Caffeine intake – Excessive caffeine intake can cause sleep problems, particularly if you're having trouble sleeping already. Similarly, some medications (both over-the-counter and prescriptions) contain ingredients such as painkillers and antihistamines that may interfere with sleep quality
  • Alcohol consumption – Alcohol is a depressant which means it depresses the central nervous system and brain, making it harder to get that restorative sleep we need. Even if you fall asleep faster and stay asleep longer, the quality of your sleep may still be poor because alcohol reduces rapid eye movement (REM) and deep sleep stages.
  • Nicotine intake – Nicotine is a stimulant which means it speeds up brain function and can make it hard to fall asleep. Similarly, it can also make it difficult to stay asleep because nicotine is a stimulant that hampers the ability of the body to repair itself during sleep
  • Medications – There are plenty of medications approved by doctors which could cause insomnia symptoms. Some examples include hormonal contraceptives, heartburn medications, certain asthma inhalers, and even corticosteroids.

What is the Best Time Range for Quality Sleeping?

The best time to go to bed is between 10 and 11 pm. A recent study conducted by UK Biobank suggests that our circadian rhythm is best suited for sleep between the hours of 10 pm to midnight. Researchers Shahram Nikbakhtian, Angus B Reed, Bernard Dillon Obika, Davide Morelli, Adam C Cunningham, Mert Aral, and David Plans concluded that deviations from this schedule could reduce sleep quality significantly, and increase the risk for cardiovascular disease, especially among women.

However, keep in mind that this study is based on mainly recollection-based data collection, which can be difficult to verify given our forgetful nature as humans. The best time to sleep may be subjective.

Some people can go to bed at midnight regularly and wake up feeling fresh and ready for the day early in the morning, while others may need to get in bed at 10:00 pm just so they can get a good night's sleep. The time range that you should aim for is between 7-9 hours/night. Although this will vary depending on your age, activity level, and hormone levels

The best way to ensure you're getting a good night's sleep is to follow a regular schedule of going to bed and waking up at the same time every day. This helps establish a rhythm that trains your body clock to know when it's time for sleep and when it's time for wakefulness.

What are the Reasons for Poor Sleep Quality?

Factors that lead to poor sleep quality include but are not limited to the following:

  • Fitness level – If you aren't exercising regularly, it may be harder for your body to wind down at night. So try to work some physical activity into your daily routine if you have trouble falling asleep at night. Also, avoid strenuous exercise too close to bedtime. This will help keep your heart rate steady when you go to sleep, which in turn will help your body fall asleep faster.
  • Age – As we age, our circadian rhythm becomes more rigid and less adaptable to changes in routine that may lead to sleep disturbances. This is why older adults are more likely to have difficulties falling asleep. Our internal clock also becomes weaker and the production of cortisol and melatonin – two hormones that play a vital role in sleep regulation – diminishes with age.
  • Hormones – Females tend to have more irregular hormone levels than males, especially during their menstrual cycle. This hormonal fluctuation throughout the month may lead to sleep disturbances which can be made worse by stress levels. In general, women experience more sleep disturbances than men, but this can be managed with changes in daily habits and lifestyle choices.
  • Diet – According to studies conducted by Richard Wurtman and Judith Wurtman (who are both doctors at the Clinical Research Center of the Massachusetts Institute of Technology), we produce less serotonin as we age, which can lead to poor sleep quality. Serotonin is converted into melatonin so eating foods high in protein and carbohydrates before bed can help keep your serotonin levels steady at night.
  • Smoking – Nicotine, a main ingredient of cigarettes, is a stimulant that can cause you to have difficulty falling asleep. If you are having trouble sleeping, it may be a good idea to quit smoking. If you can't, try not to smoke at least 2 hours before bedtime and preferably not within 1 hour of going to sleep
Illustration of a Woman Thinking about Food

What Diseases can cause Poor Sleep Quality?

Here you can see the possible diseases that can cause poor sleep quality.

  • Hypothyroidism – Hypothyroidism is a condition in which the thyroid gland cannot produce enough of its hormone thyroxine, which plays an important role in regulating our body's clock. A lack of thyroxine can lead to chronic fatigue and sleep disturbances because it prevents your body from being able to regulate its circadian rhythm.
  • Heart disease – People who have heart failure or other conditions that cause heart arrhythmias may find it difficult to fall asleep because of the changes in their heart rate. Their hearts may beat rapidly for a while and then too slow, which makes it hard for them to get comfortable enough to sleep through the night.
  • Cancer – Cancer treatments often lead to problems with sleep. People who are undergoing chemotherapy or radiation treatments often experience fatigue, insomnia, loss of appetite, depressed moods, and pain – all symptoms that can negatively affect sleeping patterns.
  • Diabetes – According to a study conducted by Harvard Medical School, people with type 2 diabetes have a higher risk of sleep apnea. Sleep apnea is one of the most common medical causes of sleep problems.

It occurs when your breathing is interrupted while you sleep and it can lead to other health problems as well as daytime fatigue.

How to Improve Sleep Quality

Improving sleep quality is not as difficult as it sounds, especially if you aren’t dealing with a sleep disorder that requires medical intervention. In some cases, it may be as simple as forming better sleep habits.

  • Get physically active – Getting regular physical activity can lead to better sleep quality because it helps tire your body, which means you'll be more inclined to fall asleep faster. Try going for a walk at night or sign up for an exercise class if you don't already have a fitness routine. You can even just do some simple exercises right in your bedroom to help tire your muscles before you sleep, however it’s a good idea to allow a few hours to pass between exercise and sleep, as too much stimulation can actually delay your sleep.
  • Manage stress – High levels of stress have been shown to cause problems with sleeping patterns, so managing your stress is one of our best tips to increase sleep quality. Everyone has some level of stress in their lives and there are ways that you can try to ease the amount that you have, such as meditation, yoga, and deep breathing. Avoiding caffeine, alcohol, and heavy meals at least a few hours before bedtime can also help.
  • Keep a sleep schedule – Going to bed and waking up at the same time every day can be a key factor in improving your sleep quality. Try going to bed about 30 minutes earlier each night until you fall asleep easily, and you'll soon have a better idea of when you should start getting ready for bed.
  • Fix any problems in your bedroom – Having a comfortable sleep environment is key to falling asleep faster and maintaining good sleep quality. We spend a third of our lives in our bedrooms, so it's important that the air is clean and filtered and that the temperature is just right. You can also try using a white noise machine or playing calming music before bed.
Kids Exercising Before Bed Illustration

What items do you need for a night of good sleep?

Items that can help improve your sleep quality include:

  • Comfortable mattress and pillow – Most mattresses should last between 7 and 10 years, depending on how well you take care of them. You can extend the life of your mattress by rotating them monthly – turn them head-to-foot so the weight is distributed evenly throughout their life. However, if your mattress is sagging or causing you pain, it may be time to invest in a replacement.
  • Air filter – if you're having trouble breathing or allergies are a problem at night, an air filter could help you breathe more clearly. Keep in mind that too much cold air can also cause your breathing to be interrupted, which leads to poor sleep quality
  • White noise machine – A white noise machine can mask pesky noises that keep you awake, but it can also provide a calming routine that lulls you to sleep, training your mind to know when it’s time for rest.
  • Eye mask – An eye mask can also help reduce stimulation to your mind from light, and become an important part of your sleep routine. Additionally, it can help signal to your mind that it’s time to stop using your cellphone, and relax.
  • Earplugs – If white noise isn't doing the trick, you may want to invest in a pair of moldable earplugs to drown out the sound of traffic, pets, or a snoring partner.
  • Weighted Blanket – A weighted blanket can be helpful for people who suffer from insomnia or other sleep problems because of anxiety. When you lie down under the weighted blanket, it provides a calming pressure on your body called deep pressure stimulation (or DPI) that mimics the feeling of being held by someone else – which is generally something we associate with feelings of safety and calm.

Of the must-have products for better sleep on this list, a mattress will probably make the most significant difference in your sleep environment, as it's literally the foundation of good sleep. While it may be a large investment initially, it always pays off in the increased sleep quality and significant health benefits associated with resting well.

Girl listening to music with a sleeping mask on

Jill Zwarensteyn is the editor for Sleep Advisor and a certified sleep science coach. She is enthusiastic about providing helpful and engaging information on all things sleep and wellness.

Based in Los Angeles, she is an experienced writer and journalist who enjoys spending her free time at the beach, hiking, reading, or exploring new places around town.

She’s also an avid traveler who has a personal goal of being able to successfully sleep on an airplane someday.

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