Sleep research has long been studying the relationship between cortisol and the quality and patterns of sleep. Cortisol plays a key role in the sleep-wake cycle. Disruptions to healthy cortisol levels can severely interfere with sleep and contribute to sleep disorders, and prolonged sleep deprivation or poor sleep cycles negatively affect our cortisol levels. It is possible to encourage healthy cortisol levels, discourage negative cortisol spikes, and in turn positively affect your sleep and overall health.
Cortisol is known as the body’s primary stress hormone. It is a stimulating, alerting hormone urged on by a complex network that incorporates elements of the central nervous and adrenal systems. In the presence of an imminent threat or intense stressor, cortisol is responsible for stimulating the body’s natural flight-or-fight response. Although this is the role we are most aware of and familiar with, cortisol does much more than drive that flight-or-fight mode. This important hormone has a number of other functions in our body, such as regulating blood pressure, influencing and reducing inflammation, balancing our blood sugar levels, regulating energy levels, contributing to the cardiac system function, and of course, helping to control the sleep-wake cycle.
More often than not, we hear about how harmful cortisol is. This is in large part because cortisol contributes to weight gain, and if you’re trying to learn healthy ways to lose weight, you’re probably reading or hearing a lot about lowering your cortisol levels to maintain a healthy weight. There’s no question that chronically elevated cortisol levels do contribute to weight gain and sleep disruptions, both of which affect each other negatively and create a vicious cycle of stress, poor sleep, and weight gain or weight stagnation. Although cortisol is responsible for these negative effects, it’s important to be clear that cortisol is also an essential component of human physiology, and the challenge many of us face is simply to keep cortisol levels from getting too high. Chronically elevated cortisol levels can cause a number of health problems in addition to those listed above. These include high blood pressure, diabetes, heart disease, chronic fatigue, memory loss and difficulty focusing, increased inflammation leading to greater vulnerability to illness and accelerated aging, poor digestion, and mood disorders such as depression and anxiety.
Cortisol is part of our brain’s complex system known as the hypothalamic-pituitary-adrenal axis, also known as the HPA axis, which combines parts of the central nervous and endocrine systems. Cortisol is produced in our adrenal glands, while the hypothalamus and pituitary glands (in our brains) monitor our cortisol levels and alert the adrenal system to adjust cortisol production as needed in response to our immediate circumstances. This communication produces cortisol and regulates the functions of the body from our sleep-wake cycles to mood to digestion to immune function. Long story short, this is a super important hormone.
Cortisol works together with our sleep-facilitating hormone melatonin to regulate sleep and wakefulness. These two hormones working together ensure that when it gets dark, you start to feel sleepy, and when the sun hits your eyelids, you begin to wake (hopefully, feeling rested). If you suffer from prolonged, chronic stress, then you risk this network becoming constantly activated, constantly signaling the adrenal system to produce more and more cortisol, which in turn makes it more difficult to fall asleep and stay asleep, or to get into periods of deep sleep, which we absolutely need in order to really be rested when we wake.
Just like almost all of the hormones in the human body, cortisol has a daily, 24-hour rhythm, and cortisol levels are generally at their highest in the morning. Usually at around 9:00 am, if you want to get specific. Cortisol levels begin to gradually elevate during the second half of our sleep cycle and then proceed into a rapid rise when you get up before peaking at around that 9:00 am mark. From there, cortisol levels go into a gradual decline throughout the day and reach the lowest level around midnight. Your bedtime is the time when the HPA axis activity is at its lowest level, which is why you naturally begin to feel tired at around this time. This is how cortisol plays a crucial and critical role in our sleep-wake cycle, and the morning-high to evening-low rhythm is accurate for most chronotypes.
When this cortisol rhythm is thrown out of balance, it leads to sleep and health problems, and prolonged sleep and health problems can lead to chronic disease. There are simple adjustments you can make to lower this stress response and help create a healthier you. Some of the most basic of these are things any doctor would tell you to do: practice regular, light-to-moderate exercise, take some time to practice deep breathing and mindfulness with exercises such as yoga, take supplements such as krill oil, magnesium, and vitamins (although you should always ask your doctor before starting any supplement regimen), and changing the way you wake up!
Remember when I said that your cortisol production is at its peak between your wake-up time and 9:00 am? Well, if you’re waking up to a loud, jarring alarm clock, chances are you’re starting your day with way more cortisol than you should be. If you’re woken by an alarm that sounds like a siren or a car alarm, you’re immediately putting your body into flight-or-fight mode before you even take in your surroundings. That’s a terrible way to start your day. Not to worry, there are gentler alternatives to give you a calmer, more peaceful start to your day. One of those is to use a sleep-tracking app that has a gentle wake-up alarm. These play a pleasant tune starting at a low volume that gradually grows louder until you turn it off. You can also invest in a Tempur-Pedic Ergo ProSmart base with SleepTracker AI, snore response, sleep coaching, and soundscape mode. The features of this base will help you drift off more peacefully, ensure you stay asleep by stopping your partner’s snoring, and will help you wake up feeling more refreshed and rested so your cortisol levels aren’t so elevated right when you wake up. King Koil also has an ultra-comfortable, straight-out-of-the-future smart bed called the Smart Life which features a gentle wake-up function. This causes the mattress itself to gently wave under your body, which brings you out of your sleep cycle naturally, rather than disrupting it with noise. Waking up to gentle motion rather than sound is the best way to start your day with the exact right cortisol level to carry you through the day without undue agitation, irritability, fatigue, or stress.
Given all of this information (and I know it’s a lot!), what can you do right now to improve your sleep-wake cycle and your day-to-day life? One thing you can do is call to speak with a Sleep Expert who can help you get a better mattress and a futuristic base to ensure you get better sleep and wake up to a better day.