A circadian rhythm is a roughly 24 hour cycle in the physiological processes of living beings, including plants, animals, fungi and cyanobacteria. In a strict sense, circadian rhythms are endogenously generated, although they can be modulated by external cues such as sunlight and temperature. Circadian rhythms are important in determining the sleeping and feeding patterns of all animals, including human beings. There are clear patterns of brain wave activity, hormone production, cell regeneration and other biological activities linked to this daily cycle.
"Sleep is a consequence of circadian rhythms,"
While circadian rhythm disruption may be common among some, the research suggests that it may be contributing to a host of diseases that may be prevented by regulating things such as sleep/wake patterns and times of eating to help prevent circadian rhythm disruption.
In mammals, the internal clock that maintains circadian rhythm is essential for normal physiological functions. The rhythms can, however, be disrupted, and deregulation of circadian rhythm is associated with many disorders, including metabolic disease and neuropsychiatric disorders including bipolar disorder, anxiety, depression, schizophrenia and sleep disorders.
Many people have their circadian rhythms disrupted on a regular basis -- shift workers like nurses, doctors, firefighters and policemen. "Other people have 'social jet lag,' a lifestyle pattern that leads them to maintain a normal schedule on weekdays, but then stay up late and sleep in on the weekends. Most circadian rhythms are controlled by the body's biological "clock." This clock, called the suprachiasmatic nucleus or SCN is actually a pair of pinhead-sized brain structures that together contain about 20,000 neurons. The SCN rests in a part of the brain called the hypothalamus, just above the point where the optic nerves cross. Light that reaches photoreceptors in the retina (a tissue at the back of the eye) creates signals that travel along the optic nerve to the SCN. Signals from the SCN travel to several brain regions, including the pineal gland, which responds to light-induced signals by switching off production of the hormone melatonin.
The SCN is located just above the optic nerves, which relay information from the eyes to the brain, so it is ideally positioned to receive information about the amount of incoming light. When there is less light, such as after sunset, the SCN directs the brain to produce more melatonin, a hormone that makes you sleepy. In this way, the master clock directs our sleep-wake cycles.
The body's level of melatonin normally increases after darkness falls, making people feel drowsy. Melatonin is thought to act as the body's clock-setting hormone. The longer a person is in darkness the longer the duration of melatonin secretion. Secretion can be diminished by staying in bright light. Melatonin also appears to trigger the need to sleep.
A person's internal body clock lies in the brain's hypothalamus and is called the Suprachiasmatic nucleus (SCN).
The SCN also governs functions that are synchronized with the sleep/wake cycle, including body temperature, hormone secretion, urine production, and changes in blood pressure. By depriving people of light and other external time cues, scientists have learned that most people's biological clocks work on a 25-hour cycle rather than a 24-hour one. But because sunlight or other bright lights can reset the SCN, our biological cycles normally follow the 24-hour cycle of the sun, rather than our innate cycle. Circadian rhythms can be affected to some degree by almost any kind of external time cue, such as the beeping of your alarm clock, the clatter of a garbage truck, or the timing of your meals.
When there is less light, such as after sunset, the SCN directs the brain to produce more melatonin, a hormone that makes you sleepy. In this way, the master clock directs our sleep-wake cycles.
Treatment options for circadian rhythm disorders vary based on the type of disorder and the degree to which it affects the individual’s quality of life. Behavior Therapy such as maintaining regular sleep-wake times, avoiding naps, engaging in a regular routine of exercise, and avoiding caffeine, nicotine, and stimulating activities within several hours of bedtime is important in the treatment of circadian rhythm disorders. People who have a circadian rhythm disorder respond well to light therapy.
Today, we are living in a light-deprived world and are paying for it with our health. We’re in the office or store by eight am in the morning, on the run all day – mostly inside – then back at home – inside again – glued to the artificial light or the pc monitor. Some call this “progress” – and to be sure, in many ways it is. But the problem is we’ve progressed faster than we’ve evolved – so it is no wondering that so many of us are suffering the effects of this new ‘indoor’ existence. We evolved to spend most of our waking hours outside, in the bright sunshine – but today our lifestyles are causing us to fight what Mother Nature intended for us by living in the dark.
Many people with total blindness experience life-long sleeping problems because their retinas are unable to detect light. These people have a kind of permanent jet lag and periodic insomnia because their circadian rhythms follow their innate cycle rather than a 24-hour one. Daily supplements of melatonin may improve night-time sleep for such patients. However, since the high doses of melatonin found in most supplements can build up in the body. Long-term use of this substance may create new problem, because the potential side effects of melatonin supplements are still largely unknown, most experts discourage melatonin use by the general public.
Light therapy is a medical treatment that consists to expose the eyes to light of a specific intensity and visible spectrum very close to that of sunlight. In most cases, treatment is recommended every day for a given length of time depending on the indication. The beneficial effect of light is linked to its physiological action particularly its influence on secretion of melatonin, the “sleep hormone,” and serotonin, a neurotransmitter.
Re-Timer provides a UV-free green light source shown in university trials to be the optimal wavelength to re-time the circadian rhythm, allowing you to achieve a sleep rhythm that is in your own control.