Zzz: Why Sleep Matters (Part 1 of 2)

To be completely transparent, I’ve struggled with sleep for as long as I can remember. It usually takes me forever to fall asleep. I could never nap as a kid and I still can’t. My sleep schedule is certainly not consistent. A part of me feels like I shouldn’t be giving sleep advice since my sleep isn’t perfect. However, it is precisely because I have experienced poor sleep that motivates me to find solutions for better sleep for all of us.

First of all, why should you care about getting high quality and a sufficient quantity of sleep?

After all, if you’re chronically sleep deprived it’s easy to underestimate how much lack of sleep affects you. Ignorance is bliss right? Right? Well…maybe not.

The short answer: Sleep impacts quite literally every system and cell of the body. Lack of sleep is associated with increasing your risk of:

A heart attack and/or stroke
Blood sugar dysregulation and type 2 diabetes
Decreased markers of fertility
Lowered immune system activity
Gene dysregulation
Decreased attention span
Increased emotional reactivity
And poor mental health just to name a few

Even the Guinness Book of World Records will no longer recognize records for sleep deprivation because it is considered that dangerous!

The long answer: If you’re like me and you want to dig further into the nitty-gritty science of how sleep (or lack thereof) impacts your body, here is what I learned from reading “Why We Sleep” by neuroscientist Matthew Walker PhD. For even more information, I highly recommend reading his book. Knowing exactly how sleep impacts my body is very motivating for me to improve my sleep.

Skip to my post on tips for better sleep.

The Human Sleep Cycle

The human sleep cycle is approximately 90 minutes, starting with 3 stages of non-rapid eye movement sleep (NREM), followed by rapid eye movement sleep (REM).

NREM sleep is important for physical repair, declarative memory consolidation, and motor-skill improvement.

In contrast, REM sleep helps us increase creativity, problem-solving, and emotional processing in particular.

Interestingly, during the beginning of the night we spent most of our time in NREM sleep punctuated by brief stints in REM sleep. However, halfway through the night the ratio reverses and we spend more time in REM sleep and significantly less in NREM. T

hough scientists are still trying to figure out why this shift happens, what is clear is that if you go to bed too late you miss important NREM sleep whereas if you wake up too early you miss critical REM sleep.

Sleep and Whole Body Health

Cardiovascular Health

One study tracked healthy adults with no previous cardiac conditions over many years and found those that slept 5 or 6 hours (or less) per night had a 200-300% increased chance of developing atherosclerosis compared to those who slept 7-8 hours per night (Walker, p. 166).
Research suggests that those who are over 45 and who sleep less than 6 hours a night have a 200% increased risk of having a heart attack or stroke (Walker, p. 165).
According to a Japanese study that included 4,000 male participants over 14 years, the people who slept less than or equal to 6 hours per night had a 400-500% higher risk of having a cardiac arrest (even when the researchers controlled for other factors) compared to those who slept more than 6 hours (Walker, p. 165).
A growth hormone that repairs your blood vessel lining is turned off with lack of sleep, whereas normally the hormone increases at night while you sleep (Walker, p. 168).
Lack of sleep puts us in a fight-or-flight state (Walker, p. 167).
Even one night of sleeping 1 or 2 hours less can increase blood pressure (Walker, p. 166).
Inadequate sleep can decrease HDLs cholesterol, the “good” cholesterol (Walker pg. 188).

After daylight savings and people lose an hour of sleep there is a noticeable increase in heart attacks the next day whereas in the fall when we gain an hour of sleep when the time changes, heart attacks notably decrease the next day (Walker, p. 169).
While it may be difficult to prove direct causation between insufficient sleep and cardiovascular problems, current research suggests a strong relationship between the two.

Metabolism and Blood Sugar

In one study participants who had no existing diabetes or blood sugar problems were forced for 6 nights to sleep for only 4 hours per night. After those 6 nights the participants had a 40% reduction in their ability to absorb glucose due to being less sensitive to insulin compared to when they got adequate sleep prior to the study (Walker, pg. 170-171).
Another study by Van Cauter found that people were hungrier when they only slept 4-5 hours per night compared when those same participants slept 8.5 hours per night (Walker, pg. 172). Physical activity was held constant.
Not enough sleep increases ghrelin, a hormone that tells you you’re hungry, and decreases leptin, a hormone that tells you you’re full (Walker, pg. 173).
People tend to have more cravings for sugary foods, simple carbohydrates and salty snacks when sleep deprived. This is thought to be because the prefrontal cortex, which is the part of your brain that helps you make well-thought decisions, is less active when you’re sleep deprived (Walker, pg. 175).
Adequate sleep is thought to improve your microbiome because, without sleep, extra cortisol promotes the growth of negative bacteria (Walker, pg. 176-177).

Reproductive System

Lack of sleep decreases testosterone, decreases sperm count, and increases sperm deformities. Low testosterone is associated with decreased energy and difficulty focusing. Adequate testosterone helps maintain and build muscles, strength, and bone density (Walker, pg. 179).
Sleeping less than 6 hours per night regularly is associated with a 20% decrease in follicular-stimulating hormone in women which is needed for ovulation (Walker, pg. 180). Ovulation has many physical and mental health benefits beyond reproduction. More on this in a future blog post.
A study on women who worked night shift found a 33% increase in menstrual cycle irregularities compared to those awake during the day. Night shifters were also more likely to experience fertility issues (Walker, pg. 180).

Immune System

Just one night of 4 hours of sleep decreases circulating natural killer cells by 70% compared to getting 8 hours of sleep (Walker pg. 184).
In one study people were purposely exposed to a cold virus. Among participants who slept 5 hours per night on average, 50% were infected after being exposed. However, 18% of the participants who slept at least 7 hours per night on average were infected (Walker, pg. 182).
Your body creates a stronger immune reaction to the flu shot when you are well-rested with at least 7-9 hours of sleep the week before. Sleeping extra after getting the flu shot to make up for low sleep still won’t get you to the same level of immune response as being well-rested before (Walker pg. 183).
A European study found that sleeping 6 or fewer hours per night is associated with a 40% greater risk of cancer (Walker, pg. 185).
M1 macrophages that help fight cancer are decreased with lack of sleep while M2 macrophages, which increase cancer growth, are increased with lack of sleep (Walker, pg. 186).

Gene Regulation

Lack of sleep can dysregulate gene expression (Walker, pg. 187).
In one study, healthy participants were limited to 6 hours of sleep per night for 1 week and at the end of the week there were 711 gene regulation abnormalities compared to the same participants when they got 8.5 hours per night (Walker, pg. 187). The genes that were impacted were those that regulate chronic inflammation, cellular stress, metabolism and the immune system (Walker, pg. 188).
Lack of sleep is associated with damaged telomeres, a marker of aging, though it’s not known if this is a causal relationship yet (Walker, pg. 188).

The Brain and Attention Span

Human performance decreases after 16 hours of being awake (Walker, pg. 140).
Greater than 7 hours of sleep per night is needed to maintain our cognitive abilities (Walker, pg. 140).
Sleeping 7 hours per night for 10 days is equivalent to pulling an all-nighter in terms of cognitive performance. This has huge implications for how we function in our daily lives, including our driving performance. Driving while sleep-deprived is so incredibly dangerous, especially considering that most people underestimate how tired they actually are.
One study that tested participants’ concentration with an attention span task found that participants who experienced 10 days of 6 hours of sleep performed just as poorly on the task as people who stayed awake for 72 hours straight. Compare this to the group who slept 8 hours every night during the study who showed no change in performance. Even after 3 days of sleep recovery, participants in the sleep-deprived groups were not able to perform as well as their baseline performance pre-sleep-deprivation. (Walker, pg. 136)
People tend to underestimate how sleep-deprived they are when they are sleep-deprived, especially when that is their baseline that they have normalized (Walker, pg. 137).

Emotional health

Lack of sleep is associated with emotional reactivity: In one study, half of the participants slept a full night while the other half was kept awake all night. Both groups were shown pictures the next day, including pictures that had emotional content while undergoing an MRI scan. The amygdala, which is activated with strong emotions and feelings of fight-or-flight was 60% more activated in the sleep-deprived group than the sleep group (Walker, pg. 147). This is thought to be because sleep helps the prefrontal cortex communicate with the amygdala (Walker, pg. 147).
Areas of the brain associated with rewards and impulsivity are hyperactive in people who lack sleep (Walker, pg. 148).
Not enough sleep is also associated with bullying, aggression, and other behavior issues both in children and in prisons (Walker, pg. 148).
I don’t know about you, but when I’m sleep deprived I certainly notice myself being more emotionally sensitive than I might otherwise be.

Mental health

There is a bidirectional relationship between lack of sleep and mental health issues, poor mental health can lead to poor sleep, and poor sleep can cause people without mental health issues to have brain activity similar to those with mental health problems (Walker, pg. 149-150).
Certain genes help control both sleep and the circadian rhythm and these gene are not normal in people with mental health issues, suggesting a connection between sleep and mental health (Walker, pg. 150).

Enough about the scary ways lack of sleep impacts us. Let’s focus on how adequate sleep can make us feel better.

Early research suggests that dreams play a role in healing emotional wounds, help us accurately read emotions in other people when we are awake, increase creativity, and improve memory (Walker, pg. 206-234).
REM sleep helps us regulate our emotions and grow in our emotional intelligence (Walker, pg. 74).
Sleep improves our problem-solving abilities (Walker, pg. 228-229).
Our attention span, motivation, alertness, and focus are all increased with adequate sleep.
Sleep promotes tissue repair, wound healing, healthy blood glucose levels, a strong immune system, and a better ability to cope with stress.

I don’t know about you, but after I learned just how much quality sleep effects me down to a cellular level, I felt incredibly motivated to prioritize my sleep. So naturally I did a deep dive into the simple habits I could implement to improve my sleep.

Click here for 16 Tips for Better Sleep

In our fast-paced society with ever increasing demands on our time, it’s easy to prioritize everything but sleep. However, the research is clear that sleep is a key pillar of all our health. Our cardiovascular, metabolic, immune, and nervous systems as well as our mental and emotional wellbeing is improved with adequate sleep. One of the most concerning aspects about lack of sleep is how easily our bodies adapt and normalize lack of sleep. We then underestimate our sleep deprivation and how much that impacts our functioning. My challenge to both you and myself is to prioritize our sleep and, hopefully in the process, discover how much better we feel.

What helps or hinders your sleep? What do you do to prioritize sleep? What differences in yourself do you notice when you are well rested?

Sources

Abbasi, B., Kimiagar, M., Sadeghniiat, K., Shirazi, M. M., Hedayati, M., & Rashidkhani, B. (2012). The effect of magnesium supplementation on primary insomnia in elderly: A double-blind placebo-controlled clinical trial. Journal of research in medical sciences: the official journal of Isfahan University of Medical Sciences, 17(12), 1161–1169.

Blum, D. (2023, February 27). How a consistent sleep schedule might protect your heart. The New York Times. https://www.nytimes.com/2023/02/15/well/mind/sleep-schedule-heart-health.html

Curtis, L. (2023, June 27). Which types of magnesium are good for sleep? Verywell Health. https://www.verywellhealth.com/magnesium-for-sleep-7501514

Huberman, A. (2021). Toolkit for sleep. Huberman Lab. https://www.hubermanlab.com/newsletter/toolkit-for-sleep

Huberman, A. (Host). (2022, August 8). Sleep toolkit: Tools for optimizing sleep & sleep-wake timing. (No. 84). [Audio podcast episode]. In Huberman Lab. Scicomm Media. https://www.youtube.com/watch?v=h2aWYjSA1Jc

te Kulve, M., Schlangen, L.J.M., & van Marken Lichtenbelt, W.D. (2019). Early evening light mitigates sleep compromising physiological and alerting responses to subsequent late evening light. Scientific Reports 9, 16064 (2019). https://doi.org/10.1038/s41598-019-52352-w

Walker, M. (2017). Why we sleep: Unlocking the power of sleep and dreams. Simon & Schuster, Inc.