Circadian Rhythm Disorders | Sleep Health Foundation

The term circadian comes from the Latin phrase “circa diem,” which means “approximately a day.” Circadian rhythms work by helping to make sure that we can maintain a regular pattern across a 24-hour period. The term ‘circadian rhythm’ is not exactly the same thing as the term ‘body clock’. Internal biological clocks help regulate the timing of bodily processes. So, in other words a circadian rhythm is an effect of a biological clock rather than being an actual body clock.

Circadian rhythms are closely connected to the 24-hourcycle of night and day. The circadian rhythms throughout the body are connected to an internal clock located in the brain. It is found in the suprachiasmatic nucleus (SCN), which is in a part of the brain called the hypothalamus. The SCN is sensitive to light, and this is why light is so central to the regulation of our sleeping patterns. While other cues, like exercise, work patterns, social activity, and temperature, can affect the internal clock, light is the most powerful influence on circadian rhythms.

There are many times when the circadian system and the internal biological clocks can be out of synch and this can lead to sleeping difficulties and poor quality of life. Disruptions to circadian rhythm can occur due to behaviours such as travel and working non-standard hours. Health experts have identified a number of types of circadian rhythm sleep-wake disorders (CRSWD) based on their characteristics and causes.

Jet Lag: This occurs when a person travels across multiple time zones in a short period of time. Until a person’s circadian rhythm can acclimate to the day-night cycle of their new location, they are likely to suffer sleeping problems and fatigue from jetlag.
Shift Work Disorder: Work obligations can cause major disruptions in a person’s circadian rhythm. Work which requires having to work through the night and sleep during the day, puts a person’s sleep schedule directly at odds with the local daylight hours.
Advanced Sleep Phase Disorder (ASPD): People with this rare type of disruption find that they get tired early in the evening and wake up very early in the morning.
Delayed Sleep-Wake Phase Syndrome (DSWPD): This type of circadian rhythm disruption is associated with staying up late at night and sleeping in late in the morning. It is not unusual for adolescents to begin experiencing a delay to their circadian rhythm from about 11-12 years of age.