Stress Test

Sleep Test 101

Aspects of your sleep cycle

An estimated 60 million Americans persistently suffer sleep deprivation. And 70 percent of adults experience enough daily stress to the point it disrupts their nightly sleep. To better understand sleep troubles, it's important to know how your body's sleep cycle works. The alternating cycle of sleep and waking is directly related to the levels of two key hormones: melatonin and cortisol. Understanding the fluctuations of these two hormones during the day and how they relate to one another can help you determine why you are experiencing difficulty sleeping.

How the two biomarkers we measure impact your health

Melatonin

Melatonin, the hormone that helps regulate the body's internal biological clock, is produced in the pineal gland, a pea-sized gland in your brain. During the day, the pineal gland is inactive, but when the sun goes down, it becomes activated and begins to produce melatonin. Typically, your melatonin level peaks around bedtime, stays elevated throughout the night, and then falls back to its daytime level in the morning.

Melatonin is known as the "Dracula of hormones" because your body naturally produces melatonin in response to darkness, and production is "shut off" by bright light. The feedback between your body and the environment is the primary way your body knows when it should be asleep or awake. In other words, your melatonin level directly impacts your sleep cycle by inducing and maintaining normal sleep.

If melatonin does not rise properly at night, or if its production is disrupted by light or other factors, then you can experience the symptoms of sleep deprivation.

A low level of melatonin in the evening/night is related to the following symptoms: difficulty falling asleep at night, waking up during the night, waking up too early, not feeling rested, and daytime tiredness or sleepiness.

On the other hand, if your melatonin level is higher than the normal range in the morning/daytime, then you can experience fatigue, grogginess, or reduced core body temperature.

Many things can disrupt your sleep cycle, including stress, dietary factors, medications, the environment, your work schedule, and the amount or timing of light exposure ‐ including exposure to light from blue screens.

Cortisol

If melatonin is the "nighttime" hormone, then cortisol can be thought of as your "daytime" hormone. It is a key adrenal hormone that balances melatonin. Your cortisol level should be highest shortly after waking up and should then fall throughout the day. If cortisol does not follow its normal cycle, then your sleep and health can be adversely affected.

Cortisol plays many roles in the body, but it has a special relationship to sleep. Cortisol follows a cycle that is opposite of melatonin's and, in this role, it is responsible for signaling the body to be awake and responsive. Your cortisol level should be at its lowest late at night (when melatonin levels are high) and should have a peak shortly after you wake up in the morning.

The morning peak of cortisol helps "prepare you for the day" by:

• Raising your blood sugar, giving you energy, and probably making you hungry for breakfast
• Increasing your metabolism and getting you ready to be active
• Preparing you for the upcoming stressors of the day

Cortisol's daily rhythm can become unbalanced due to chronic stress related to emotions, lifestyle, diet, health issues, overtraining, and other causes. Although there are more than one kind of abnormal pattern, the most common abnormal patterns for cortisol are explained below.

When cortisol's level is too high, then your body feels "on" all the time. You can have disturbed sleep, excessive hunger, weight gain, and an anxious mood. A too-elevated level of cortisol can impair your body's ability to absorb nutrients from food because cortisol tells your body to stop producing the enzymes needed for digestion. A consistently clinically high level of cortisol can signal a medical condition that should be managed by an endocrinologist.

When cortisol's level is too low, it could indicate that your adrenal glands are persistently depleted and unable to meet the demands that your body puts on them. As a result, you can feel fatigued all the time, have low mood, get sick more frequently, have challenges with pain and inflammation, and have a hard time responding to normal stress. If your cortisol level is abnormally low persistently, then it can be a sign of a medical condition that should be managed by an endocrinologist.

The Science

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Kessler K, Hornemann S, Rudovich N, et al. Saliva samples as a tool to study the effect of meal timing on metabolic and inflammatory biomarkers. Nutrients 2020 28;12(2):340. doi: 10.3390/nu12020340.