Circadian Rhythm

Circadian Rhythm Disorders

Daily and seasonal changes of daylight

Daily and seasonal changes in light intensity drive most of your automatic and hormonal body functions. They influence the ‘internal clock’ – the circadian rhythm. One obvious response of this ‘clock’ to light changes is to regulate the sleep-wake cycle. But amongst other functions, it also controls the rhythmic fluctuations in body temperature, mood and behaviour.

sundialThe production of the hormone melatonin in the pineal gland, a small and specialized organ in the brain, varies with daylight hours. The gland is most active at night and least active at day. The hormone informs other body parts of the length of daylight and darkness periods and of the light intensity. The body reacts appropriately to the environmental circumstances with, for example, tiredness or a change in body temperature.

In October 2000, the New England Journal of Medicine published a study in which scientists tested melatonin supplements on a small group of blind people. This group of people suffered from sleep disorders because they could not distinguish between light and dark. After taking the supplement, the majority of the participants developed normal sleep cycles.

But you don’t have to be blind to disrupt your biological clock. Air travel and irregular shift work confuse the sleep-wake cycle resulting in either jet lag or sleep problems. Treatment with melatonin supplements may help.


Jet lag symptoms and remedies

Jet lag, also jetlag or jet-lag, medically referred to as “desynchronosis” is a physiological condition which is a consequence of alterations to circadian rhythms; it is classified as one of the circadian rhythm sleep disorders. Jet lag results from rapid long-distance transmeridian (east-west or west-east) travel, as on a jet plane.

The condition of jet lag may last many days, and recovery rates of 1 day per eastward time zone or 1 day per 1.5 westward time zones are mentioned as fair guidelines.

The symptoms of jet lag can be quite varied and may include the following:

Loss of appetite, nausea, digestive problems
Headache, sinus irritation
Fatigue, irregular sleep patterns, insomnia
Disorientation, grogginess, irritability
Mild depression

Since the experience of jet lag varies among individuals, it is difficult to assess the efficacy of any single remedy. Gradual adjustment over the course of several days of the onset of sleep while maintaining its regular length of 7-8 hours can reduce fatigue and prevent depression. When the goal is to catch-up with local time (vs. fallback to), this can be aided by avoiding afternoon naps and eating an early and carbohydrates-rich, low-protein dinner.
Source: Wikipedia

Seasonal Affective Disorder

Grey and rainy days make a mockery of UV radiation-related skin and eye disorders. ‘Skin cancer because of sunlight? I don’t even know what the sun looks like,’ you joke. The sun-related dangers to your health are less, but instead your mood declines with every grey day. You are lethargic and you long for hibernation rather than work. You are a victim of the ‘winter blues’.

Light plays an important role in the biological rhythm of humans. For you, this syndrome may be nothing else than the cause for a bad mood and hopefully doesn’t affect your daily life. But up to 5% of people living in areas with seasonal low light suffer from the more serious seasonal affective disorder (SAD).

Well, here is something you really want to blame on the weather. Oversleeping, lethargy, weight gain, craving for sweets are some of the mild symptoms of SAD or the ‘winter blues’. For some, however, the disorder can also show itself in severe depressions. The very unfortunate are no longer able to work effectively and lose all interest in social activities.

The disorder affects women more often than it does men: about three-quarters of all patients are women of all age groups. Less daylight during winter appears to be the major trigger of SAD, rather than short-term dull weather. Some very sensitive persons experience the symptoms also in spring and summer during cloudy days and even inside poorly lit buildings.

Variations in light intensity alter hormone levels. In the evening the level of melatonin increases, but drops off again in the morning. During the day, the level of serotonin hormones is at its peak. But which hormone is ultimately to blame for depressive mood changes is still unclear.

If a lack of light can create such problems then bright light should prevent it. Many cultures from latitudes with long winters must know this. They light bonfires to drive away the ‘evil spirits’, or go on vacations to sunnier places. A little more sophisticated and effective are modern light therapies. Many patients respond well to short periods of high-intensity light exposure. In most cases the next spring or summer brings back the energy and a happy mood.

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