What is a circadian rhythm disorder?

Most people naturally wake up with daylight and fall asleep once it gets dark. This natural cycle is regulated by the circadian rhythm, a true internal clock located in the hypothalamus, a region of the brain. The circadian rhythm also influences several biological functions, such as blood pressure, body temperature, and mood [1].

Sleep disorders related to the circadian rhythm are caused by an occasional or ongoing disruption of sleep patterns. This disruption can result from internal factors, such as brain damage, blindness or hormonal changes, or from external factors that affect the timing and duration of sleep:

• Engaging in intense physical activity within three hours before bedtime
• Festive nightlife
• Jet lag
• Hospitalization or bed rest
• Lack of exposure to sunlight
• Night shifts or variable hours
• Certain medications

Out of sync with a normal sleep-wake cycle, affected persons may sometimes have to deprive themselves of sleep in order to meet their social or professional obligations. For example, a young person who always goes to bed late because of a circadian rhythm disorder may have to get up early for classes, reducing total sleep time. This sleep debt is often the cause of severe fatigue; a loss of concentration, attention and energy; and mood disorders.

Recent studie suggest that circadian rhythm disruption may also be associated with mental health problems, such as depression and bipolar disorder [1,2].

Advanced sleep phase syndrome: This disorder is more common in the elderly . Falling asleep and waking up occur much earlier (at least two hours, often more) than the normal schedule. Although they may have a normal amount and quality of sleep, people with this disorder have difficulty staying awake early in the evening (6 p.m. to 9 p.m.) and wake up early (2 a.m. to 5 a.m.).

Irregular sleep-wake syndrome: This disorder is characterized by variable sleep periods. Sleep is fragmented into short periods throughout the day and night. Overall, persons may get a normal amount of sleep, but the fragmented nature of the sleep can be disruptive and affect social life. It more often affects the elderly, especially in nursing homes where they have little exposure to time cues such as natural light, daily activities and structured schedules.

Free-running syndrome: This disorder, also known as hypernycthemeral syndrome, causes falling asleep and waking up to be continuously and progressively out of sync with the normal cycle by about 15 minutes. The sleep-wake pattern is not tied to the 24-hour cycle, but to a slightly longer period. This means that affected individuals fall asleep and wake up a little later each day. This disorder is more common among blind people because daylight usually helps regulate the sleep-wake cycle.

Shift work sleep disorder: This disorder mainly affects people who work nights or variable hours. Because their work hours do not always match their circadian rhythm, they may experience an irresistible urge to sleep on the job and an inability to sleep when needed. When they do sleep, the quality of their sleep is often poor, leading to fatigue, exhaustion, headaches, concentration problems and irritability. It is estimated that at least a quarter of workers with non-standard hours suffer from this disorder. [3]

Jet lag: Jet lag occurs when a person crosses more than three time zones. Because the person’s internal clock is still based on the original time zone, he or she may experience a strong urge to sleep during the day and an undesirable level of alertness at bedtime. This disorder is temporary. It is estimated that the body needs one day to adjust to each time zone crossed. Jet lag can affect anyone who travels by plane, but the symptoms can be more severe and last longer when a person travels eastward and in older people in general.

Polysomnography, on the other hand, is a more comprehensive test conducted either in a sleep lab or at home. It is often used when a combination of sleep disorders is suspected.

Salivary melatonin levels are another indicator used to assess circadian rhythm. This method involves measuring the level of this hormone, which plays a key role in regulating sleep.

Light therapy: It involves exposure to light that mimics natural daylight (2,000 to 10,000 lux), the duration and timing of which vary according to the type of disorder. This therapy is particularly beneficial for shift workers, helping to regulate their disturbed circadian rhythm.

Our sleep hygiene program identifies the need and provides clear instructions on how to use light therapy.

Medication: Taking melatonin, a hormone that helps regulate the circadian rhythm, may be useful in promoting sleep.

Circadian rhythm disturbances can profoundly disrupt not only sleep, but also the body's overall balance. People affected sleep at inappropriate times or have difficulty maintaining a regular sleep schedule. The result: excessive fatigue during the day, insomnia at night... and sometimes much more. A dysregulated body clock can also lead to imbalances in body temperature, hormone production and even quality of life, causing irritability, nausea or depression [9].

We offer services that can assist your doctor in diagnosing sleep disorders and determining the appropriate treatment.

• Sleep care services
• Sleep hygiene program
• Online boutique

Do you have a medical prescription for one of these tests? Book an appointment online or contact Biron Health Group’s customer service at 1 833 590-2712.