Do you have a Circadian Rhythm Sleep Disorder?


Sleep should be a natural human activity, done without thought and without difficulty. However, many people have problems with their sleep patterns, that affect their overall wellbeing and their ability to function effectively during the day. Scientists are beginning to study these problems closely to determine ways to correct them, and this is leading to increased interest in circadian rhythms.

What are circadian rhythms?

Circadian rhythms are physical, mental, and behavioural patterns or rhythms such as eating, sleeping, migrating, and mating, that follow a daily cycle and are found in most living things, including animals, plants, and even microbes. Just like animals, humans have evolved to react to external and environmental cues, known aszeitgeber’, in order to survive. The main cue influencing human circadian rhythms is daylight, so being awake during the day, and sleeping at night is an example of a light-related circadian rhythm.


When the normal cues for physical functions are absent or slightly out of sync, the disruption can adversely affect the restorative action of sleep, and negatively effect mood, hormone levels, body temperature and mental acuity. These are critical activities that allow human beings to continue to engage in the broad range of physical and mental activities required during their waking hours.

What are biological clocks?

Biological clocks are an organism’s innate timing device. They’re composed of specific molecules (proteins) that interact in cells throughout the body, and are found in nearly every tissue and organ. Researchers have identified similar genes in people, fruit flies, mice, fungi, and several other organisms that are responsible for making the clock’s components, and help to regulate sleep patterns, feeding behaviour, hormone release and blood pressure.

Are biological clocks the same thing as circadian rhythms?

No, but they’re related. Biological clocks produce circadian rhythms and regulate their timing.

What is the master clock?

A master clock in the brain coordinates all the biological clocks in a living thing, keeping the clocks in sync. In vertebrate animals, including humans, the master clock is a group of about 20,000 nerve cells (neurons) that form a structure called the ‘suprachiasmatic nucleus’, or SCN, which is located in the hypothalamus. It receives information about incoming light from the optic nerves, which relay information from the eyes to the brain, and when there is less light, such as at night, the SCN tells the brain to make more melatonin – which makes us drowsy.

How is the Pineal Gland involved?

Once called the 'third eye,' the pineal gland is a small gland located deep in the centre of the brain. Named for its pinecone shape, it was one of the last brain organs to be discovered, and has been the subject of much mythology and speculation. The seventeenth-century French philosopher Rene Descartes thought the soul was located in the pineal gland. In fact, it is from here that melatonin is produced, and then released at night when it’s dark, which points to melatonin's role in sleep. Many supplement manufacturers offer melatonin as a ‘natural’ sleep aid, however, research carried out in 2016 found that removing the pineal gland did not affect the activity levels of rats that had normal access to light and dark. They concluded that the function of the pineal gland may be more complicated than initially thought and that its role may vary widely between different animals. You can find the full report here:

How do researchers study circadian rhythms?

Scientists learn about circadian rhythms by studying humans or by using organisms with similar biological clock genes, such as fruit flies and mice. By altering the subject’s exposure to light and darkness, they look for changes in gene activity or other molecular signals. They may also study organisms with irregular circadian rhythms to identify which genetic components of their biological clocks may be broken.

The term ‘circadian’ was first coined by Franz Halberg in the late 1950s derived from latin ‘circa’ meaning ‘about’ and ‘dies’ known as ‘day’, thus, referring to rhythms that cycle with a period length of about a day. The study of circadian rhythms is called chronobiology.


Prize-winning research

Jeffrey Hall, Michael Rosbash and Michael Young won a Nobel prize in 2017 for their discoveries explaining how plants, animals and humans adapt their biological rhythm so that it is synchronised with the Earth’s revolutions. They identified a gene within fruit flies that controls the creatures’ daily rhythm, known as the ‘period’ gene, which encodes a protein within the cell during the night, which then degrades during the day. Hall and Rosbash then went on to unpick how the body clock actually works, revealing that the levels of protein encoded by the period gene rise and fall throughout the day in a negative feedback loop. Young, meanwhile, discovered a second gene involved in the system, dubbed ‘timeless’, that was critical to this process. Only when the proteins produced from the period gene combined with those from the timeless gene, could they enter the cell’s nucleus and halt further activity of the period gene. Young also discovered the gene that controlled the frequency of this cycle. See his lecture on the subject here:

Do circadian rhythms affect health?

Yes. Circadian rhythms can affect several important bodily functions including sleep-wake cycles, hormone release, and body temperature. Biological clocks that run fast or slow can result in disrupted or abnormal circadian rhythms, and irregular rhythms have been linked to several chronic health conditions, such as sleep disorders, obesity, diabetes, epilepsy, depression, bipolar disorder, drug and alcohol addiction, and seasonal affective disorder. Understanding what makes our biological clocks tick, and the effect on our health when our circadian rhythm is out of sync, is key to developing treatments for the various physical and mental health disorders that have been linked to its misalignment. You can find further information here:

The chronobiology of sleep

Sleep is an important part of whole body health. Not only will a good night’s rest make us feel better, it will also make us healthier as well. Like other creatures, human beings sleep to rest their bodies. However, in humans, the mind also uses this time to unwind from events experienced whilst awake. The alternate periods of light and darkness as the days pass helps to regulate our inner clocks to induce sleep patterns. However, certain factors can disrupt natural sleep/wake cycles. A large number of people now live and work in 24-hour environments, spending many more hours indoors, exposed to artificial light, and eating late into the night. All of which can have a detrimental effect on sleep cycles. Those who work the night shift or have changing shift patterns are at far greater risk of long-term sleep problems than people who have regular work schedules and are able to divide their day into distinct periods of alertness and rest. The elderly and infirm also have difficulty maintaining healthy sleep patterns because of a lack of activity, medical condition, medications or metabolic changes. Poor quality sleep can cause fatigue and napping during the day, further reinforcing the disrupted cycles.

What are the effects of a lack of sleep?

Healthy sleep helps to reduce normal stress levels in the body. People deprived of sleep can experience severe disturbances in brain function, including hallucinations, and even minor disturbances in normal sleep cycles can cause a variety of debilitating effects over time. Sleeplessness has been associated with higher rates of accidents, memory problems, obesity, depression, lowered libido, and poor judgment, and is linked to more serious health problems such as heart disease, diabetes, high blood pressure and stroke.


How light affects sleep

Most people have a circadian rhythm that is around 24.15 hours, roughly matching with the length of our days. This allows us to sleep and wake in tune with the natural cycles of our planet. People with a circadian rhythm that is not 24 hours suffer from a variety of problems beyond the simple inability to sleep. They can be tired constantly, yet unable to sleep at the appropriate time, which leads to symptoms such as sleeping at odd hours, brain fog, depression and learning difficulties. These people may also have less responsive immune systems and be more susceptible to diseases associated with a lack of quality sleep such as heart disease and diabetes. This disorder is especially common in people who are completely blind, because they’re unable to sense light and attune their circadian rhythms to light-dark cycles. In fact, 70 percent of people who are totally blind have it, together with a small number of sighted people.

Sleep and the immune system

Illnesses such as chickenpox and measles are associated with childhood because most people will only catch them once. The reason for this, and the efficacy of vaccines as well, is due to our immune memory. When a bacteria, virus or other invader enters our body, specialised immune cells engulf and overpower it, and in a person with a healthy immune system, this memory will last a lifetime. Thereafter, every time this same type of bacteria or virus enters our body, the memory T cells will recognise and eradicate it before it can cause illness. However, research suggests that people who get insufficient deep sleep, also known as slow wave sleep, have fewer of these protective memory T cells in their bodies, resulting in poorer immune function and increased susceptibility to illnesses, including the common cold. You can find further information here:

Can a damaged biological clock be repaired?

Whilst there is no cure for misaligned circadian rhythms, some people find that melatonin supplements enable them to get to sleep at the right time, and if the person is not completely blind, light therapy may be useful. Eating meals at the same time each day and following a regular daily exercise regime can be an effective strategy, and a new pharmaceutical drug called Hetlioz is showing promise. You can find further information here:

Thank you for reading this blog post. If you have any thoughts to share, or ideas for future posts, please do let me know. I would love to hear from you.

Thomas HallComment