Circadian Rhythm: Your Body’s Sleep-Wake Cycle
Have you ever wondered why you feel sleepy or energetic or with a poor body rhythm at certain times during the night or day, almost every day of your life? Why does the body naturally feel tired at night and active in the morning? Well, this is due to a mechanism called Circadian Rhythm – body’s sleep clock. The Circadian rhythm not only regulates your sleep-wake cycle but also supports several body functions. Read on to know how to reset your sleep clock!
What is Circadian Rhythm/Body Clock?
Circadian Rhythm is actually your body’s internal clock that runs in the background of the brain and oscillates between sleep and wakefulness. It is also referred to as the sleep-wake cycle and signals your body when you need to rest or work.
How is circadian clock different from the biological clock?
Each of these clocks has a different mechanism. The circadian clock, a molecular mechanism that results in a circadian rhythm pertaining to the daily 24-hour rhythm of the sleep-wake cycle of the body. On the other hand, the biological clock governs the circadian rhythm as well as other physiological processes of the body. These include aging, menstrual cycle, and female fertility among others.
How do the Circadian Rhythm work?
Our brain’s hypothalamus comprises of a “master clock” made up of around 20,000 neurons forming a structure known as the suprachiasmatic nucleus (SCN). It is this master clock that controls our circadian rhythm. Though our body produces circadian rhythms by natural factors, they are also affected by external stimuli. Daylight is the most important factor affecting our circadian rhythms, turning on and off our genes that control our internal clock.
For example, at night when it’s dark, your eyes send a signal to the hypothalamus that it’s time to feel tired. The brain, in turn, sends a signal to your body to release melatonin, which makes your body tired. In short, this sleep clock dictates our body the best time to sleep and wake up.
How do the Circadian Rhythm influence our health and body?
The circadian rhythm affects the body in different ways.
Erol Fikrig, professor of epidemiology at the Yale School of Medicine, said in a press release, “It does appear that disruptions of the circadian clock influence our susceptibility to pathogens”. The cycle of waking and sleeping is a natural response by your body as to when it’s time for what. So, by following the body’s natural sleep clock it has been seen that it boosts your body’s immunity and keeps your body alert and active, thus keeping you healthy.
Blood Sugar levels
The circadian rhythm influences the levels of insulin and the counter-regulatory hormones which work against the action of insulin. The counter-regulatory hormones such as glucagon, epinephrine (also known as adrenaline), growth hormone (somatotropin) and cortisol raise your blood glucose (sugar) levels when needed. In the middle of the night, there is a spike in the amount of growth hormone released by the body, followed by a rise in cortisol, which increases blood glucose production by the liver.
In people who don’t have diabetes, increased insulin secretion by the pancreas controls these processes. This keeps blood glucose levels relatively stable. However, in people with type 1 diabetes, the pancreas does not produce enough insulin and in people with type 2 diabetes, the liver may not respond to insulin well enough to stop glucose production. This changes the blood glucose levels during sleep which has a powerful effect on your morning blood glucose levels.
The cells of your muscles contain hundreds of tiny power stations, called mitochondria, which keeps you energized. Your internal sleep clock controls these energy mini-factories telling them when to release energy. These powerhouses are at peak production during the day, providing you with the energy required for your daily activities. If you do not follow your body’s circadian rhythm, you might face several sleep problems. You may find yourself wide awake at an unnatural time or sleepy when you’re not supposed to be.
Illness and well-being
Our body’s hormone production is majorly controlled by the circadian rhythm. Even the cells in the body grow faster during certain hours of the day. The body in response to the sleep clock releases the hormone called melatonin, which may improve outcomes in critical illnesses through its chronobiological, anti-inflammatory, anti-microbial, and antioxidant properties.
Melatonin is a hormone that helps to suppress harmful free radicals in your body which can cause cancer. Melatonin also slows the production of estrogen. Less production of melatonin may disturb the circadian rhythm, which makes your body more susceptible to cancer.
What happens when the circadian rhythm dysfunctions?
Circadian rhythm sleep problems arise when there is a misalignment between the timing of the circadian rhythm and the external environment or when there is a dysfunction of the circadian clock.
The following health risks are common with circadian rhythm disruption –
People with clinical depression show disrupted circadian rhythms across brain regions according to a new study published in May 2013 in the journal Proceedings of the National Academy of Sciences. Researchers looked at post-mortem brain samples from mentally healthy donors and compared them with those people who had major depression at the time of their death and found that activity of genes in the brains of depressed people failed to follow healthy 24-hour cycles.
We usually sleep in a dark environment. This is essential for melatonin production as it improves the cells’ abilities to repair oxidative DNA damage. Oxidative DNA damage can generate cancer-causing mutations.
In a 2016 study by Parveen Bhatti, Ph.D., from Fred Hutchinson Cancer Research Center, subjects who slept during the day while working at night showed lower levels of biomarker 8-hydroxydeoxyguanosine in their urine. A high presence of this chemical compound is an indication that cells have been repairing damaged DNA. Lower levels of this chemical is a sign that their cells could be more susceptible to cancer-causing mutations.
The circadian clock controls your daily cycle of sleep and wakefulness by alternately inhibiting and exciting different parts of the brain by regulating the release of certain neurotransmitters. In order for you to retain the information, your brain stimulates the hippocampus (a part of the brain).
Circadian rhythm disruption or its improper functioning may releases too much Gamma-Aminobutyric Acid or GABA (a neurotransmitter). Excess GABA affects your brain, reducing its ability to retain new information leading to short-term memory problems.
Disruption to your sleep clock or circadian rhythm may result in weight gain. Research shows that less sleep affects the production of metabolic hormones that regulate satiety and hunger. For example, when you have sleep problems, your body decreases the production of leptin, a hormone that signals your brain that the food intake is enough. At the same time, there is an increase in the production of ghrelin, a hormone that triggers hunger.
Diabetes and heart disease
Both too much sleep or a lack of it can increase your risk of type 2 diabetes. A 15-year study of more than 1,000 men found that those getting less than 6 hours or more than 8 hours of sleep had a significantly increased diabetes risk. A similar association was also observed between sleep and coronary heart disease.
Therefore, it is important that you consistently get 7-8 hours of sleep daily to reduce your risk of diabetes and heart diseases.
Other Chronic Diseases
According to a report in the Journal of the American Medical Association (JAMA), lack of sleep can increase the risk of serious and chronic diseases such as Parkinson’s, Alzheimer’s, multiple sclerosis and various gastrointestinal disorders.
How to manage your Circadian Rhythm better?
Following the body’s natural response is the best way to avoid any disruption in the sleep-wake cycle. However, sometimes due to certain conditions or illness, our body is unable to follow the healthy cycle.
Below are some of the ways in which you can manage your Circadian Rhythm:
- Follow a fixed time for going to bed and waking up to regularize your sleep-wake cycle.
- Engage in a regular routine of exercise. However, avoid exercise or any other vigorous activity before bedtime.
- Avoid consuming caffeine, nicotine, and other stimulating activities before bedtime.
- Minimize exposure to light in the evening and during the night by reducing indoor lights.
- Avoid blue light screens. Mobile phones and computer screens emit blue light which does not allow you to follow your natural sleep order. Hence, minimizing the use of laptops or mobile phones at least 1 hour before sleep can help restore your sleep cycle.
- You can use melatonin-containing medicines to adjust and maintain your sleep-wake cycle.