Our circadian rhythms control our wake-sleep cycles. However, there is much more that is known about the health conditions involved in a disruption of the natural and normal wake time and need to sleep. Recently more research has evolved in the relationship between just that cycle.

The system that regulates an organism’s innate sense of time and controls known as the circadian rhythms is called a biological clock. It is composed of proteins encoded by thousands of genes that switch on and off in a specific order. A master clock coordinates all the biological clocks in an organism.

The human master clock is a large group of nerve cells that form a structure called the suprachiasmatic nucleus (SCN). Among other functions, the SCN controls production of the hormone melatonin based on the amount of light the eyes receive. In the evenings, a person’s master clock tells their brain to make more melatonin, causing sleepiness. The SCN also synchronizes the circadian rhythms in different organs and tissues across the body.

In 2017, NIGMS-funded researchers Jeffrey C. Hall, Michael Rosbash, and Michael W. Young won the Nobel Prize for their circadian rhythms research. They identified a protein in fruit flies that has a role in controlling normal daily biological rhythms. During the daytime, this protein (called PER) is produced by the cell but immediately broken down in the cytoplasm, keeping PER protein levels low. When night falls, a protein called TIM binds directly to PER, protecting it from breaking down. The PER-TIM complexes enter the nucleus and stop the cell from making additional PER. Then, a day breaks, the PER-TIM complexes break down, the block on PER transcription is lifted, and the cycle repeats.

In this way, PER regulates its own synthesis through a negative feedback loop. Feedback loops are coordinated systems that link the output of the system to its input. For example, a thermostat functions on a feedback loop. This is similar to a home’s furnace will turn off when the house reaches the set temperature and only turn back on when the temperature falls below that threshold again.

Microorganisms, fruit flies, zebrafish, and mice are often the research organisms that scientists study because they have similar biological clock genes as humans.

Various experiments in fruit flies advance the study of the molecular mechanism underlying circadian rhythms and their effects on behavior.

Health Effects That Contribute to Circadian Rhythms Disruption

Circadian rhythms can fall out of sync with the outside world due to factors in the human body or environment. For example:

Variants of certain genes can affect the protein that control biological clocks.

Neurological diseases, such as Alzheimer’s disease, can disrupt circadian rhythms, causing poor sleep quality and changes in symptoms from day to night.

Travel between time zones (jet lag) and shift work alters the normal sleep-wake cycle.

Light from electronic devices at night can confuse biological clocks.

Drowsiness, poor coordination, and difficulty with learning and focus may occur when circadian rhythms fall out of sync short term. Long term sleep loss and continually shifting circadian rhythms can increase the risks of obesity, diabetes, mood disorders, heart and blood pressure problems and cancer, can also worsen existing health issues.

Hormones

Hormones like melatonin and cortisol may increase or decrease as part of your circadian rhythm. Melatonin is a hormone that makes you sleepy, and your body releases more of it at night and suppresses it during the day. Cortisol can make you more alert, and your body produces more of it in the morning.

Other hormones that play a role in alertness and circadian rhythm include:

• vasopressin
• acetylcholine
• insulin
• leptin

Other Factors

Body temperature and metabolism are also part of your circadian rhythm. Your temperature drops when you sleep and rises during awake hours. Additionally, your metabolism works at different rates throughout the day.

Other factors may also influence your circadian rhythm. Your rhythm may adjust based on your work hours, physical activity, stress and anxiety, and additional habits or lifestyle choices.

Age is another factor that influences your circadian rhythm. Infants, teens, and adults all experience circadian rhythms differently.

Babies

Newborns do not develop a circadian rhythm until they are a few months old. this can cause their sleeping patterns to be erratic in the first days, weeks, and months of their lives. Their circadian rhythms develop as they adapt to the environment and experience changes to their bodies.

Teens

Teenagers experience a shift in their circadian rhythms known as sleep phase delay. Unlike in their childhood years with early bedtimes around 8 or 9 p.m., teenagers may not get tired until much later in the night.

Melatonin may not rise until closer to 10 or 11 p.m. or even later. That shift also results in a teenager’s need to sleep later in the morning. Their peak sleepy hours at night are from 3 to 7 am – or maybe even later – but they still need the same amount of sleep as children.

Adults

Adults should have a pretty consistent circadian rhythm if they practice health habits. Their bedtimes and wake times should remain stable if they follow a fairly regular schedule and aim for 7 to 9 hours of sleep every night. Adults likely get sleepy well before midnight, as melatonin releases into their bodies. As adults, we reach our most tired phases of the day from 2 to 4 a.m. and 1 to 3 p.m.

Circadian Rhythms Sleep Disorders

Delayed Sleep Phase Disorder can occur in “night owls” when the preferred time for sleep is typically after 2 a.m. with wake up time after 10 in the morning. This results in difficulty falling asleep and waking up at times conducive to school and work. When the individual attempts to wake up and waking up at times conducive to school and work. When the individual attempts to wake up earlier, they become sleep deprived and alertness may be impaired. This condition is most common in adolescents.

Advanced Sleep Phase Disorder is more common in older adults who are sometimes referred to as “morning larks” when the internal clock prefers early times for sleeping and waking. This makes it difficult to stay awake through the evening hours and people who have this kind of circadian rhythm sleep disorder often wake up much earlier than desired.

Irregular Sleep Wake Disorder is most commonly seen in elderly patients with dementia and refers to a lack of rhythm in a person’s sleep and wake cycle. Sleep occurs irregularly throughout a 24-hour period. The individual cannot sleep through the night and has difficulty maintaining wakefulness during the day.

Free-running disorder or non-24 hour sleep-wake disorder is rare and seen more commonly in individuals with blindness. Bright morning light (sunrise) aligns our internal clock to the 24-hour day. when light perception is absent, the sleep period drifts later and later each day, causing this disorder.

Jet Lag happens during air travel when we pass through time zones faster than our body clocks can adjust. This causes a mismatch between the preferred sleep and waking times and the destination sleep and waking times.

Shift work sleep disorders is due to an unconventional work schedule that causes you to remain awake during preferred sleep times and, the available time for sleep occurs when your body prefers to be awake. As a shift worker you experience sleepiness while at work and insomnia during the time you have available to sleep. You may also experience difficulty concentrating, headaches, and low energy levels while awake.

Can Sleep Disorders Be Treated?

Treatment for circadian rhythm disorders effectively and offer treatments such as:

• Appropriately timed bright light exposure
• Melatonin
• Sleep scheduling and
• Other behavioral modifications.

While melatonin is not yet FDA approved, it can be beneficial for circadian rhythm sleep disorders under the supervision of specialized sleep medicine physicians.

I have found that melatonin needs to be taken in small amounts. Too much can leave you groggy and waking up with a headache. Start with small dosages.

If you are interested in finding a sleep disorder clinic call 734-936-9068. Or ask your doctor.