Counting Sheep

With only 24 hours in a day, it can sometimes be an inconvenience knowing that you should probably sleep for about a third of that time. Our need for sleep does vary throughout our lifetimes since younger children need more sleep than adults. The need for sleep even varies among people, with some individuals functioning fine on less than 6.5 hours of sleep per night (thanks to a genetic predisposition), even though most people need 7-9 hours. Despite this variation, it’s no surprise that a significant proportion of people across the world get less sleep than they need. This is concerning because a lack of sleep is associated with a variety of chronic health conditions. Based on a 2020 survey of 13,000 people representing 13 different countries, the average adult gets only about 6.9 hours of sleep on weeknights. So, this week we’re going to take some time to look at our human need for sleep, factors that affect our ability to sleep, and some insights into how other organisms “sleep”. Hopefully this article doesn’t end up putting you to sleep… well, unless you really need to get some shut-eye. Then I suppose that would be a good thing?

The Need for Sleep

The longest time that anyone has gone without sleep (on record) is ELEVEN DAYS, set by a 17-year old boy in California named Randy Gardner. Granted, that was back in 1964, and Randy Gardener is still alive today at around 75 years old. Not bad. I definitely would not recommend attempting this, though. 

During sleep, you cycle between a few different stages of sleep. These sleep stages are typically classified as either Rapid Eye Movement (REM) sleep or non-REM sleep. Non-REM sleep is further broken down into about 3 or 4 different levels based on how “deep” the sleep is. 

Non-REM stage 1 sleep is considered the “lightest” sleep and covers the transition between being awake and being asleep, which is usually only about 5-10 minutes. 

The second non-REM stage (stage 2) lasts a bit longer, and your body temperature begins to lower and eye movement pretty much stops during this stage. 

The third stage of non-REM sleep, if we’re just considering three non-REM stages, is the deepest stage of sleep where your heart and breathing rates slow down to the lowest levels during sleep. This stage of sleep occurs more during the first half of the night (in the case you do get 8 hours of sleep). 

REM sleep first occurs about 90 minutes after you fall asleep, and this stage of sleep actually mostly occurs during the second half of the night. Heart rate and blood pressure return to levels that closely resemble waking levels, and this stage is when most of your dreams occur! During this time of REM sleep, your body will temporarily paralyze your arms and legs to prevent you from acting out your dreams. 

A somewhat typical sleep cycle from falling asleep to waking up. Sleeping less than 8 hours means that you cut off a larger proportion of REM sleep as compared to non-REM sleep.

A somewhat typical sleep cycle from falling asleep to waking up. Sleeping less than 8 hours means that you cut off a larger proportion of REM sleep as compared to non-REM sleep.

One thing to consider is that shirking on sleep means that you miss out on a much greater proportion of REM sleep since the REM stage mostly occurs during the second half of an 8-hour night of sleep. REM sleep can be just as important as non-REM, so sleeping less than 8 hours (or however much your body needs) can cause a greater imbalance than you might think. 

Though you should allow yourself to cycle through the sleep stages for a full night of sleep, it’s clear this does not happen for many people. As mentioned earlier in this article, a sleep study from 2020 actually placed the average amount of sleep at 6.9 hours per weeknight for 13,000 respondents representing 13 different countries. This study was performed by the company Philips, and a similar study is performed by them each year to compare any changes and observe trends in sleep patterns. Pretty cool. The thing is, the inadequate amount of sleep varies among the population based on a few different factors. You can even see some stark contrasts in the amount of sleep people get throughout the United States based on geographic location. 

Percentage of people reporting less than 7 hours of sleep on average. I don’t know about you, but it looks like people in Kentucky don’t sleep too much.

Percentage of people reporting less than 7 hours of sleep on average. I don’t know about you, but it looks like people in Kentucky don’t sleep too much.

This issue of short sleep duration even varies among demographic groups, with a higher proportion of black and Pacific Islander/Hawaiian individuals in the United States getting less than 7 hours of sleep per night as compared to other races/ethnicities.

So what does a lack of sleep do to us? A simple introductory example is seen with a mundane, yet extraordinarily consistent example of sleep deprivation that occurs each year: daylight savings time. In the spring when we lose an hour of sleep due to daylight savings, there is a 24 percent increase in heart attacks. In the fall when we gain an hour of sleep, there is a 21 percent decrease in heart attacks. Now, there are a number of other potential causes for this pattern, but there is also other evidence that suggests sleep deprivation is associated with ill health. 

A 2014 study conducted by the Centers for Disease Control and Prevention (CDC) showed that individuals who got less than 7 hours of sleep were significantly more likely to report chronic health conditions than those that got greater than 7 hours of sleep. The chronic health conditions included coronary heart disease, strokes, chronic obstructive pulmonary disease (COPD), diabetes, asthma, arthritis, depression, kidney disease, and cancer. Again, this is just an association, and the people that have these health conditions might just end up getting less sleep because of their health condition. Similarly, there have been associations between adequate sleep and neurodegenerative diseases such as Alzheimer’s or Parkinson’s, but again we’re still not certain whether poor sleep causes the diseases or vice versa. Researchers are working on understanding whether there is a clear cause-and-effect relationship between the sleep and these health conditions. It’s probably best to just have a healthy sleep pattern in the meantime. 

Sleep also has a major effect on cognitive abilities, and a lack of sleep is shown to impair memory, reduce the ability to make decisions, and cause lapses in attention. It also affects your moods and emotions (pretty clear from personal experience).

The circled region is the amygdala, which is a part of the brain that affects emotions. It appears much more active under the condition of sleep deprivation.

The circled region is the amygdala, which is a part of the brain that affects emotions. It appears much more active under the condition of sleep deprivation.

Perhaps it would also be a good time to introduce some more positive news by letting you know that there is a World Sleep Day that usually takes place on the second or third Friday of March each year (it was March 19 in 2021). The day is taken to raise awareness on the importance of sleep, but hopefully you can still appreciate the importance of sleep all year long. 

What Affects Sleep?

Our ability to sleep is natural, but it can still seem elusive at times. A number of factors can influence our ability to sleep and the quality of that sleep, so it’s important to take those factors into consideration when you’re trying to get the most out of your bedtime. Some of these are rather obvious…

  • Diet: Since both sleep and diet are fairly complex aspects of health, most studies simply establish associative relationships as opposed to specific cause-and-effect relationships between diet and sleep. Generally, the conclusion is that poor diet and poor sleep quality go hand-in-hand (no surprise there). Specifically, deficiencies in certain vitamins and minerals such as calcium, magnesium, and Vitamins A, C, D, E, and K have been associated with sleep problems. The thought is that a deficiency in these vitamins and minerals affects hormonal pathways that regulate our sleep-wake patterns. 

Additionally, a high-carbohydrate meal frequently makes you drowsy, but overall high-carbohydrate diets can actually harm sleep quality. Increased carbohydrate intake has been associated with an increase in the number of awakenings at night as well as a decrease in the amount of deep sleep achieved. 

Obesity, which is directly linked to diet, is also a key risk factor for obstructive sleep apnea (a serious sleeping disorder which impairs breathing).

  • Stress: Various stressors may lead to difficulty sleeping. For example, simply moving to or visiting a new location can cause short-term insomnia. Stress itself causes the release of cortisol and adrenaline which keep you alert in stressful situations, but this is not as good for proper sleep. The self-reinforcing stress-sleep cycle is a vicious cycle to get caught in. Basically, a lack of sleep results in greater levels of stress, which impairs sleep, which increases stress, and the cycle goes on. Best to focus on addressing either your sleep habits or stressors in order to break the cycle if you find yourself there. 

  • Light: Also another rather obvious one. Our body relies on light to help regulate our sleep-wake cycle. When in darkness, the pineal gland in the brain will begin to produce the hormone melatonin, which helps us to fall asleep. If your eyes detect light, though, (such as light from a computer or a lightbulb) the production of melatonin is slowed or stopped. The idea of “blue light” coming from electronics and impairing sleep is somewhat true, because blue light is a higher-energy wave that impairs melatonin more heavily than other colors of light. One Harvard study showed that, after equal periods of exposure to green and blue light, the blue light inhibited melatonin levels twice as long as green light. Don’t simply stick with other colors of light, though, because any light may have an effect. Levels of light around 10 lux (a measure of light illuminance) are shown to have an effect on melatonin. Most table lamps exceed this level of lux, and night lights have about half that level of lux.

An excerpt from an infographic based on the Philips annual sleep survey of 13,000 people. The data show that more people use their cell phone in bed compared to last year, which may reduce the ability to naturally sleep due to the extra light exposure from the screen.

An excerpt from an infographic based on the Philips annual sleep survey of 13,000 people. The data show that more people use their cell phone in bed compared to last year, which may reduce the ability to naturally sleep due to the extra light exposure from the screen.

  • Sleep Environment: The environment that you sleep in understandably has a significant effect on your ability to sleep. For one, a lower ambient temperature results in better sleep, with many researchers suggesting that 65°F is the optimal bedroom temperature for sleep (though the exact cooler temperature can vary for each person). Odors or scents can also affect your ability to sleep. Some studies have shown that the scent of lavender essential oil can improve sleep quality, and for those that routinely sleep next to someone, that person’s unique scent can improve sleep. Also, wash your sheets! A 2012 poll from the National Sleep Foundation found that a significant number of respondents were more excited to go to bed when their sheets were freshly scented. 

Of course there are other factors affecting sleep, such as an established sleeping schedule or the presence of chronic pain, but we won’t be covering those here. 

One interesting thing to note is that sleep quality is frequently scored in studies using the Pittsburgh Sleep Quality Index (PSQI). For the PSQI, the overall score can range from 0 to 21 with lower numbers indicating better sleep quality. Any number greater than 5 for overall PSQI score is considered to indicate poor sleep quality. You can take an online version of the PSQI here: https://qxmd.com/calculate/calculator_603/pittsburgh-sleep-quality-index-psqi

Sheep Sleep, Too

It’s not just humans that need sleep. The need for sleep is seen throughout the animal kingdom, and even a natural circadian rhythm is seen in plants, too. This “sleep” takes some interesting forms, though, and it can be quite different from our typical human way of sleeping.

For one, humans are monophasic sleepers for the most part, which means that the bulk of our sleep happens over one concentrated time period (nighttime). This is not the case for a number of animals. Humans in particular have this luxury because we typically don’t have to be on the lookout for predators while we sleep. Ring-tailed lemurs are also typically monophasic sleepers. They sleep in trees surrounded by their lemur troop, so they likely feel more secure against predators as they sleep. 

A troop of lemurs sleeping

A troop of lemurs sleeping

Many other animals sleep in short bursts throughout the day, so their sleep patterns are called polyphasic. This type of sleep pattern is exhibited by both cats and dogs (hence the concept of a “cat nap”). One study published in Physiology & Behavior back in 1977 showed that the dogs studied had an average sleep episode of only 45 minutes. Sleeping with a pet on your bed may not always be the best thing if you’re trying to get quality sleep, because more likely than not they’ll naturally wake up multiple times throughout the night. 

The length of sleep that different animals require varies rather greatly. Humans need about 7-9 hours per night… but check out these other sleep patterns of animals:

  • The average giraffe only sleeps about 4.6 hours per day.

  • Elephants have been recorded with a sleep time of only around 2 hours per day. Some scientists have also recorded elephants traveling for nearly two days without any sleep. 

  • Little brown bats sleep about 20 hours per day on average

  • Snakes sleep at least 16 hours per day, and this may increase to 20 hours per day after a large meal

  • Giant Aldabra tortoises can sleep up to 18 hours per day

A Giant Aldabra tortoise sprawled out and getting some shut-eye

A Giant Aldabra tortoise sprawled out and getting some shut-eye

Also, compared to other primates, human sleep is some of the most efficient sleep. Many other species of primates require greater than 8 hours of sleep per night. 

One interesting aspect of sleep for some animals is the ability to sleep unihemispherically. With unihemispheric sleep, only one side of the brain falls asleep while the other remains awake. This way, the animal gets its sleep while still remaining somewhat active enough to be alert for predators and perform basic functions. Dolphins are unihemispheric sleepers in order to be conscious enough to swim to the surface of the water for air while also sleeping. During unihemispheric sleep, the animal closes one eye to allow the associated half of the brain to sleep. Other unihemispheric sleepers include birds and crocodiles. So yes, a bird can technically be asleep while gliding around. 

Another aspect of sleep that is quite common is different forms of hibernation, which is moreso  extended periods of drastically low metabolism as opposed to true “sleep”. Many animals are capable of hibernation, including bears, bats, certain possums and hedgehogs, salamanders (whose “hibernation” is actually called “brumation”), one bird called the Common Poorwill, certain insects, and many more! Hibernation is pretty incredible in terms of decreased body temperature, oxygen intake, and heart rate in some animals. For example, a bat’s heart rate can decrease from 400 beats per minute normally down to only 11 beats per minute during hibernation. Wood frogs undergoing hibernation during the winter will literally freeze over entirely.

The Common Poorwill curled up on a rock, one of the only birds known to undergo hibernation

The Common Poorwill curled up on a rock, one of the only birds known to undergo hibernation

Plants are a bit less-studied than many animals, but there is clear evidence that they undergo some form of circadian rhythm that follows the presence of the sun. Studies have shown that at night, trees droop their branches and may release a form of plant growth hormone. During the day, plants will often open their flowers more and return to their “pre-drooped” levels. While this circadian rhythm is likely not considered “sleep”, there is still much more to explore.

Sleep is intimately related to so many aspects of our lives, and this holds true for other animals as well. As humans, we may think that 7-9 hours a night is SO LONG (or not long enough depending on your perspective), but taking that time to rest has been shown to improve our cognitive abilities and overall health. You can read a good book, meditate or pray, or simply count sheep to prepare for sleep… whatever you do, sleep is not wasted time. Sleep is time that makes the other 15-17 hours during the day more productive and meaningful. Admittedly, I should take my own advice on this matter of prioritizing sleep, but hey, nobody’s perfect, right?

To Think About…

  1. If you haven’t already, take the PQSI test to get an idea of whether you might have poor sleep quality: https://qxmd.com/calculate/calculator_603/pittsburgh-sleep-quality-index-psqi 

    If you do have poor sleep quality, what might be the reasons?

  2. How might human sleep patterns be affected by culture or location? For example, some areas of Norway have extended hours of daylight in the summer and longer nights in the winter. Other areas of the world with extreme heat might have a form of siesta where an afternoon nap is normal. 

  3. Reflect on the role that sleep plays in your life and how it affects your lifestyle, and compare this to some other animals. For example, imagine sleeping for almost 20 hours out of the day like the small brown bat!