Sleep is a vital part of our overall health and well-being. We cannot live without it. In this article, I will explain a few common theories as to why humans sleep along with why sleeping is important for health.
And of course, I’ll give you some tips on how to squeeze more quality sleep into your life.
Table of Contents
Why Do We Sleep?
There are a few interesting theories as to why humans sleep. Here, I’ll go over four of them. Even though some don’t apply to today’s world, they all make sense to me. What do you think?
Inactivity Theory
This theory is sometimes called the adaptive or evolutionary theory of sleep.
The inactivity theory suggests that we become inactive at night as a survival technique. You see, we don’t see very well in the dark, and so we are more vulnerable at night to predators (1).
This theory proposes that humans sleep to protect themselves from danger. According to the theory, this provides us with an evolutionary and reproductive advantage.
Though some may argue that sleeping puts us at a higher risk, and survival would be more likely if we stayed awake 24 hours a day. In my opinion, the inactivity theory doesn’t apply to most cultures today, as we’ve become more and more evolved.
Energy Conservation Theory
Next is the energy conservation theory. This theory proposes that the main purpose of sleep is to reduce energy needs at night when energy levels are not efficient enough to search for food (2).
This theory is backed up by research suggesting that metabolism does decrease by up to 15% while we sleep (3). Hmm, interesting. But I feel there really is more to why we sleep than simply to conserve energy.
Restorative Theory
Third, is the restorative theory of sleep. This theory hypothesizes that we sleep as a means of repairing and rejuvenating.
This includes improving our immunity, healing damage, dreaming, promoting growth and learning, removing waste, and avoiding any serious side effects of sleep deprivation (1).
It states that during sleep, our bodies repair and replete cellular components that were depleted throughout the day.
This theory does have some criticism, however. This is primarily because other organisms besides humans also sleep, including single-cell organisms and plants. So do these organisms improve learning during sleep just as we do? And do they also dream as we do?
Difficult to wrap your head around a house plant having dreams, isn’t it?
Brain Plasticity Theory
And lastly, there is the brain plasticity theory. This theory suggests that we sleep to promote neural reorganization and the growth of new neuron connections in our brain (2). It also stresses the importance of sleep stages, including rapid eye movement (REM) sleep for making these new connections and memories.
Getting an adequate amount of uninterrupted sleep is crucial for going through an entire sleep cycle and maintaining a proper circadian rhythm. This theory explains why infants and children need more sleep (up to 14 hours per day), which is because their brains are still developing neuronal connections.
Sleep and Cardiometabolic Health
Sleeping is important for health; especially cardiometabolic health.
According to the American College of Cardiology, around 47 million people in the United States have cardiometabolic disorders. This puts them at a higher risk of developing heart disease or type 2 diabetes.
Cardiometabolic syndrome is a cluster of conditions that include high blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol or triglyceride levels.
The role of sleep and the circadian system is not one to be ignored when it comes to a healthy lifestyle. Many report that sleep disruptions are linked to a range of cardiometabolic health outcomes.
One study found that short sleep duration and poor sleep quality were associated with a higher risk of developing type 2 diabetes in adults. The study analyzed data from 1,683 adults over a period of 10 years and found that those who slept less than six hours per night were more likely to develop type 2 diabetes (4).
There are also two separate studies involving large sample sizes that concluded that poor sleep quality increases the risk of developing heart failure and those who slept less than six hours per night had a higher risk of developing cardiovascular disease than those who slept six to eight hours per night (5, 6).
And last but not least, another study found that people who slept less than six hours per night had a higher risk of developing metabolic syndrome (7).
What Happens When We Don’t Get Enough Sleep?
As you can see there are many theories as to why we sleep. I personally think the best theory is a combination of them all!
Either way, getting adequate sleep allows our bodies to function at their best, both physically and mentally. When we don’t get enough sleep, it can have many negative effects on our health. Some of the most common include:
- Impaired cognitive function– When we don’t get enough sleep, our brains don’t have a chance to rest and recharge. This can lead to problems with concentration, memory, and decision-making.
- Increased risk of accidents– Sleep deprivation can lead to fatigue, which makes us more likely to make mistakes, which can lead to accidents. This is especially true when we are driving or operating machinery.
- Depression or Mood swings– When we don’t get enough sleep, our emotions can be more volatile. We may be more irritable, anxious, or depressed.
- Weight gain– Sleep deprivation can lead to changes in hormones that regulate hunger; leptin and ghrelin. This can make us more likely to gain weight (3).
- Heart disease– Sleep deprivation has been linked to an increased risk of heart disease.
- Stroke. Sleep deprivation has also been linked to an increased risk of stroke.
- Diabetes– Sleep deprivation can make it more difficult for our bodies to regulate blood sugar levels, which can increase the risk of diabetes (3).
- Immune system dysfunction– Sleep deprivation can weaken our immune system, making us more susceptible to illness.
- Cancer– Some studies have shown that sleep deprivation may increase the risk of certain types of cancer, including breast, colorectal, prostate, and endometrial cancer (8).
In addition to the above consequences, you may also experience headaches or nausea if you’re lacking sleep. There also seems to be an association between lack of sleep, diabetes, and sleep apnea, which again is quite complex, involving many hormonal changes (3).
Related article: Can Sleep Apnea Be Cured?
How Much Sleep Do We Need?
The amount of sleep we need varies from person to person, but most adults need between 7-9 hours of sleep per night. Children and teenagers need even more sleep, with younger children needing up to 14 hours per night.
| Age Range | Hours of Sleep Per Night |
|---|---|
| 18-60 years | 7 or more hours per night |
| 61-64 years | 7-9 hours |
| 65+ years | 7-8 hours |
Related article: 5 Things You Can Do to Support Heart Health NOW
How Much Sleep Do I Need Calculator?
There are a number of online calculators that can also help you determine how much sleep you need. These calculators take into account your age, gender, and activity level.
One of the most popular sleep calculators is the Sleep Foundation Sleep Calculator.
You simply enter your age range along with when you want to wake up and when you want to go to sleep.
Some sleep calculators may also ask for your activity level or sleep habits such as how often you wake up during the night and how long it takes you to fall asleep.
It is important to note that these calculators are just estimates. The amount of sleep you need varies from person to person and you should not rely solely on a sleep calculator. If you are not sure how much sleep you need, it is best to talk to your doctor.
And more importantly, if you are having trouble sleeping, talk to your doctor. There may be an underlying medical condition that is interfering with your sleep.
How Can We Get a Good Night’s Sleep?
There are several sleep behavior strategies we can practice daily to improve our cardiometabolic health and our chances of getting a good night’s sleep. These include:
- Going to bed and waking up at the same time each day, even on weekends
- Creating a relaxing bedtime routine (warm bath, reading a book, music, meditation, stretching, journaling)
- Limiting the use of electronics (or use a blue light filter) which can block melatonin production
- Making sure our bedroom is dark, quiet, and cool
- Avoiding a heavy meal before bedtime and choosing a light snack instead
- Avoiding caffeine and alcohol before bed
- Getting regular exercise
- Seeing a doctor if we have a sleep disorder
These are just a few suggestions to get a better sleep. Another alternative medicine option is using essential oils or aromatherapy to help relax you as you drift into slumber.
If you have a sleep condition like insomnia, there are therapy options that are proven to help, including cognitive behavior therapy for insomnia (9).
Foods That Help You Sleep Better
To help promote a restful night’s sleep, there are specific foods you can eat. Many of these foods are either natural sources of melatonin and tryptophan, or have other supportive components to sleep health.
- Kiwi– this fruit boosts serotonin which converts to melatonin in our bodies to help make you drowsy.
- Nuts– preferably unsalted varieties if you have high blood pressure. Eating around 1.5 ounces at night provides a good source of magnesium and zinc which can boost melatonin levels.
- Yogurt– this is an natural source of the amino acid, tryptophan, which promotes sleep. Yogurt is also a good source of protein and carbohydrates to help sleep blood sugar stable.
- Banana– this fruit contains tryptophan, along with potassium and magnesium which can prevent muscle cramping at night and relax nerves.
- Popcorn– this complex carbohydrate gives you hunger-busting fiber to get you through the night. Plus whole grains such as popcorn lead to insulin production and increases in tryptophan levels to aid in sleep. Lightly salted or unsalted air-popped popcorn will do the trick!
- Cherries– here is another amazing sleep-promoting fruit. It has high amounts of melatonin and tryptophan, specifically tart cherry varieties like Richmond, Montmorency, and English Morello. You can also drink tart cherry juice.
- Chamomile Tea– Chamomile contains the antioxidant apigenin, which can induce relaxation and sleep.
- Eggs– Eggs contain the drowsiness-inducing amino tryptophan. Try some poached, scrambled, or hard-boiled about an hour or two before bed.
For more on the health benefits of tea: Tea for Heart Health: How a Cup a Day Can Improve Your Cardiovascular Health
Best Apps To Help You Sleep
Sleep habits can also be tracked using apps that you can download on your phone or tablet. Or you can use apps to help promote relaxation as part of your bedtime routine. I personally use the BetterSleep app and find that the sounds are so soothing that I am sleeping within minutes. Here are a few popular sleep apps:
Can Lack of Sleep Cause Nausea?
Yes, lack of sleep can cause nausea. This is because sleep deprivation can lead to changes in the way our bodies process food and fluids. When we don’t get enough sleep, our bodies produce more of the stress hormone cortisol. Cortisol can interfere with digestion and lead to nausea.
Do Women Need More Sleep Than Men?
Some studies have shown that women may need slightly more sleep than men. This is likely due to hormonal changes that occur during the menstrual cycle and menopause (10).
In addition, studies show that women report poorer sleep quality with more insomnia, daytime sleepiness, and difficulty falling asleep and staying asleep than men (11).
Conclusion
There are a few theories explaining why humans sleep and why sleeping is important for health. Getting enough sleep is essential for our overall health and well-being. By prioritizing sleep health we can improve our mood, boost our energy levels, and reduce our risk of chronic diseases.
If you’re having any of the symptoms listed above and suspect it’s related to lack of sleep, I suggest trying a sleep calculator, addressing underlying health issues, or using any of the above techniques to get more sleep. And don’t forget to mention your concerns to your doctor! Managing sleep deprivation early on can prevent health issues later if properly treated. Sweet dreams! 😴
Kiran Campbell is a registered dietitian and entrepreneur with 13 years of experience. She has a degree in psychology as well as dietetics. She is also a proud member of the Academy of Nutrition and Dietetics’ and its Cardiovascular Health and Well-being Dietetics Practice Group among others. Kiran proudly presents and promotes the most up-to-date, science-based nutrition information on all things heart-related. She aims to serve not only individuals with heart disease, but also those wanting to protect against it. Learn more about Kiran by visiting her About Page.