Why Sleep Is Nonnegotiable Medicine

Even flowers (dandelions included!) close for the evening when the sun goes down. Sleep is an essential part of our being, integral to our existence. Yet, we still do not completely understand why.1 We do have some theories, and even without all the answers as to why we sleep, we do know it is important to our health—without question. One contributing theory, out of many reasons (e.g., neuron repair and regeneration), for why we sleep has evolved from newer research on the glymphatic system. That is right: Lymphatic with a “G.” This glymphatic system is within our brain, and it has a very critical job of clearing waste metabolites out of our central nervous system. The volume of this glymphatic system increases to 20% while we are asleep, compared to only 13% while we are awake.2 This means the glymphatic system is functioning more while we are asleep.

With or without the concrete answer of “why” we sleep, we still know the answer to how important it is to our health. Adequate, quality sleep is crucial to our short-term and long-term health and in preventing disease. This is nonnegotiable, and we will be discussing this throughout this article by discussing how sleep plays a major role in many critical physiological processes, including regulation of many important hormones such as TSH, leptin, cortisol, growth hormone, insulin, and more. Our society has trouble sleeping, there is no question about that. Our world moves fast, the demands are high, our stress levels are rising, and technology and screens are in use from when we open our eyes in the morning until we shut them at night. Our environment and lifestyle produce/inflict upon us stressor after stressor, to the point where genuine rest and quality sleep have become difficult, purposeful tasks that we have to carve out space and time for, and have to learn like they are a honed skill. It should not be this way, but it is.

Thyroid-Stimulating Hormone and Leptin

Studies that evaluated the effects of sleep restriction on hormones found that a lack of sleep—specifically around four hours of sleep—decreased thyroid-stimulating hormone (TSH) levels as well as leptin hormone levels.3 When leptin is low, our appetite is high. This is because leptin normally signals that we are “full” or satiated. If leptin is low, then our brain is not getting the signal that it is satisfied in terms of food/calories. This makes us feel “hungry,” and we start to crave energy-dense (aka high-calorie), nutritionally poor foods—foods that will give us quick and easy energy like simple carbohydrates (think sugars or processed foods). Thyroid health is complex, and to keep it simple, low TSH levels mean our thyroid gland is not getting stimulated enough to produce thyroid hormones that circulate in our body and carry out their actions, like supporting energy production in cells. Thyroid health and thyroid hormones are critical to have in balance, as virtually every system and hormone in our body is affected by them. It is also just as important that the rest of our body is in overall good health to respond adequately to the thyroid hormones in circulation—one major factor in achieving this is getting good sleep.

Cortisol and Growth Hormone

In stage‑3 sleep, which is also called slow-wave sleep, we are in very deep sleep, and it is difficult to wake from this.4 Getting enough good-quality sleep is critical, because in stage‑3 sleep, our body secretes growth hormone, which is important for things like physical repair and learning.5 Sleeping is one thing, but sleeping well and reaching adequate deep sleep is another, as studies have shown that growth hormone increases significantly in stage 3, compared to stages 1 and 2 or rapid eye movement (REM) sleep.6

Cortisol, one of our stress hormones, is also a key hormone in our sleep-wake cycle. Cortisol is the hormone that is supposed to spike in the morning, to wake us up and get us out of bed feeling alert and ready to tackle the day. After it spikes high in the morning, it should gradually decrease throughout the day, with a minor jump in the late afternoon, reaching its lowest levels overnight, until the next morning when it spikes up again. When this cortisol rhythm is off and cortisol is too high in the evenings/overnight, we have trouble getting restful sleep or cannot fall asleep. Specifically, cortisol reduces stage 3—slow-wave sleep 7—which in turn reduces growth hormone mentioned above, that is critical for physical repair and learning. This shows how important stress management and night-time behaviour are for getting adequate, quality sleep. Luckily for you, naturopathic doctors have a lot to offer in stress management and difficulty sleeping, and they should be your go-to practitioners for these issues.

Weight Management and the Dangers of “Belly Fat”

Quality sleep is also very important in weight management and, more importantly, in the amount of fat tissue that gets stored around our organs. This fat tissue that is stored around our internal organs is called visceral adipose tissue (VAT), and it carries many risks with it. In short, it can increase levels of inflammation, it can increase the risk of cardiovascular disease, and it is hormonally active—meaning it secretes hormones itself, leading to hormonal imbalances and a cascade of negative effects on health. People often claim they can function fine on four to six hours of sleep, but this is unfortunately not true (except for those with rare genetic chronotypes). The human body is absolutely fine-tuned to adapt for survival mode, but this does not mean it is good for you, or that it is sustainable. One study assessed the amount of VAT in both short sleepers—who slept under six hours per night—average sleepers, and long sleepers (slept over nine hours per day).8 People who slept under six hours per night or over nine hours per night accumulated significantly more VAT.9 The good news is those that changed from being a short sleeper to average sleeper protected against further VAT gain.10 This increase in visceral adipose tissue from poor sleep could be due to a few things. I discuss two possible theories, out of many mechanisms which may be occurring together or separately, below.

Poor Sleep and Weight Gain: Cortisol and the Nervous System

One theory of a mechanism for why the poor-sleep group led to increased VAT is because of how poor sleep can negatively affect cortisol management. Cortisol, when too high for too long, causes fat to be distributed viscerally—around our organs—and, over time, to become visible as central obesity, commonly referred to as “belly fat.” Research shows that nighttime cortisol concentration and sympathetic nervous system (SNS) activity increase during periods of sleep deprivation.11 This means that if we are not getting enough quality and duration of sleep, then poor sleep and the stress, anxiety, and high cortisol levels that come with it can become a vicious cycle. If your sympathetic nervous system activity is high, your body is not in a state of relaxation and is unable to facilitate or initiate sleep. Poor sleep leads to increased SNS activity, which then makes it harder to sleep the next night—this cycle continues and then continues.

Poor Sleep and Weight Gain: Leptin and Ghrelin

Another theory for the mechanism behind why people would gain more VAT with poor-quality sleep relates back to the effect that sleep deprivation has on leptin. Studies have demonstrated that sleep deprivation not only negatively affects leptin levels, as previously discussed, but also leads to the behavioural changes that are caused by these changes in leptin and other appetite-regulating hormones. This behavioural change is a consumption of higher calories.12* One study measured the levels of leptin and ghrelin in the blood of participants, and it obtained hunger and appetite ratings after periods of sleep restriction (four hours of sleep).13 The results showed that sleeping for only four hours led to decreased leptin, increased appetite and hunger ratings, and increased ghrelin levels (an appetite-stimulating hormone).14 Specifically, leptin decreased by 18% and ghrelin increased by 24%. *As a note, this is not to be interpreted that all carbs are bad, or that calorie-counting is king. This is simply to demonstrate that poor sleep can affect our appetite-regulating hormones and our behaviour, and it can make it harder for us to stick to a healthier lifestyle or our goals, as it can drive us towards consuming more processed foods and an unbalanced diet. In addition, there was a 32% increase in appetite for high carbohydrate-content food in those who slept four hours.15 These results show that when sleep-deprived, people consume more calories due to an increase in hunger and a decrease in satiety (feeling of being full).16

Insulin and Blood Sugar

Sleep is also important in ensuring proper blood-sugar regulation. When we eat, our blood sugar rises, and insulin is released to take those blood sugars and put them inside cells to control the amount of sugar in our blood. Sleep deprivation has been shown to increase both insulin resistance and inflammation.17 With insulin resistance, our body is no longer responding to that insulin as well as it used to, so both the sugars and the insulin remain high in the blood instead of being used by cells. This increase in insulin resistance is shown to be two-fold in those with misaligned circadian rhythms 18—of which shift workers would be classified into. Blood-glucose control and maintaining insulin sensitivity are an absolute key to health. These mechanisms heavily influence cardiovascular health, skin health, mood regulation, cancer incidence, brain health, eyesight, thyroid health, inflammation levels, hormonal imbalances, diabetes, heart disease, chronic disease, etc. Blood sugar and sleep are connected in both directions: Getting quality sleep is affected by blood-glucose control as well! If we do not have great control over our blood-glucose levels, they can dip low enough overnight that it causes us to have restless sleep and wake up frequently. While this article could go on and on about why sleep is nonnegotiable for health, it will not. There are varying root causes for each of the following sleep issues, and having just one of these issues is detrimental to your health:

• not sleeping seven to nine hours per night;
• not feeling rested in the morning, not feeling refreshed in the morning;
• waking up throughout the night in jolts, with anxiety, or frequently (restless);
• having difficulty falling asleep; and
• having difficulty staying asleep.

Your naturopathic doctor can help address your sleep, and because everyone is different, everyone has unique reasons for why they are having trouble getting adequate, quality sleep. Sleep is influenced by our varying hormones, digestive health, mental health, nutritional status, pain, environment during the day, behaviour during the day, environment of our home and bedroom, past trauma, current stress, activity levels, time of day of activity, what we eat, what we drink, our previous night of sleep—you get the picture. Sleep is nonnegotiable: It is a critical piece of foundational health, because it affects so many other key players in health and disease—thyroid health, immune-system health, blood-glucose control, cortisol levels and sympathetic nervous system activity, visceral fat deposition, inflammation, hormones, growth, learning, physical repair, brain health, etc. If you want to achieve better health or maintain health, you will need to sleep well. If you are having trouble sleeping well, see a naturopathic doctor.