Our daily activity and sleep rhythms are regulated by a control center in the hypothalamus region of the brain called the Suprachiasmatic Nucleus (SCN) or in layman’s terms, the body clock. The body clock needs to receive signals to tell it when to shut down and prepare for sleep and when to produce the active waking hormones. The pineal gland in the brain helps by secreting the hormone melatonin that slows us down and lets us sleep.

The most powerful signaler or ‘zeitgeber’ is bright light such as

sunshine.

Other zeitgebers are

Darkness

Certain sounds

Weather

Mealtimes.

There are many more such signals. When the body clock cannot receive these signals correctly, it malfunctions, causing circadian rhythm disorders.

Some examples for this breakdown may include the following:

Sensitivity to zeitgebers may be altered or disrupted, which can be demonstrated under certain conditions. Altered or disrupted sensitivity to zeitgebers is probably the most common cause of the circadian rhythm disorder of the sleep-wake cycle.

Disrupted pacemaker function: A dysfunction may be present in the internal coupling mechanisms of biological pacemakers, for example, the coupling of the sleep-wake cycle with the temperature cycle.

Environment: Light, higher noise levels, and elevated room temperature are not conducive to good sleep and are important variables to consider in both shift workers and night workers.

Travel: The severity of jet lag is related to the direction of travel and is more frequently seen in individuals traveling in an eastward direction. The number of time zones crossed also has an effect on the severity of jet lag, with most individuals experiencing jet lag if they cross 3 or more time zones. The rate of adjustment is 1.5 hours per day after a westward flight and 1 hour per day after an eastward flight.

Neurological disease: Alzheimer disease is one of the more common examples of neurological disease associated with a circadian rhythm disturbance; however, irregular sleep-wake cycles can also be seen in other neurodegenerative diseases. Sun downing, which is a common phenomenon in persons with Alzheimer disease, is characterized by sleep disruptions with awakenings and confusion.

Shift work: Rapid shift changes and shift changes in the counterclockwise direction are most likely to cause symptoms of a circadian rhythm disorder.

Lifestyle and social pressure to stay up late can exacerbate a circadian rhythm disorder.