Thursday, December 20, 2007

Be Your Own Sleep Aid: Circadian Rhythm And The Sleep/Wake Cycle

For all living things a wave comes in and goes out once every day. Its coming brings sleep and its departure brings wakefulness.

It's called circadian rhythm. It's a twenty-four hour cycle all humans and all creatures-- even plants and bacteria--experience without fail.

Circadian rhythm is influenced by several biological factors. If they all work in unison you sleep like a log at night and have full energy throughout the day. If they do not work together you get poor, unrestful sleep and have difficulty falling asleep.

These three factors are:

  1. body temperature variability,
  2. sleep hormone production, and,
  3. sleep pressure.

Taking correct action to get in harmony with these three biological factors is the key to getting a good night's sleep.


The Daily Body Temperature Cycle

Normal body temperature is 98.6 degrees Fahrenheit (37 degrees Celsius). However, body temperature is actually not constant, it varies by a couple of degrees throughout the day.

The graph below shows the variance in body temperature of an average healthy person over a twenty-four hour period. At times when body temperature is increasing the person feels alert and full of energy. At times when it's decreasing there is a feeling of sleepiness.

Between healthy individuals this graph may vary a little but the basic shape remains the same. (For instance, in this graph the person's peak of energy comes at about 6pm (18:00 hours). For other healthy people it could be as late as 10pm.)



Body temperature is at it's lowest point at about 4am. As dawn comes body temperature gradually increases causing the individual to awaken.

It continues to rise until noon or a little later, at which point it drops a little. Do you every feel “napish” around this time? As this graph shows, you're not alone.

At around 9 or 10pm body temperature begins to drop more and more sharply bringing on the desire for rest and sleep.

The problem many people with insomnia and sleep difficulties have--especially in a society where it's easy to be inactive--is inactivity causes a flattening out of daily body temperature variation.

This “flattening out” of body temperature variation leads to sluggishness throughout the day and poor sleep at night.

Luckily, for many people the cure for insomnia is a simple one. Twenty to thirty minutes of vigorous activity can be all that's needed to change from being a person who can't get good sleep to one who sleeps like a baby.


The Daily Sleep Hormone Cycle

The pineal gland, a gland in the center of the brain releases a hormone that causes a slight decrease in body temperature. The hormone is called melatonin.

When it's time to get up it's time for the pineal gland to stop releasing melatonin. Being in daylight causes it to stop. Being in darkness causes it to be released again.

To improve energy level and sleep quality, exposure to plenty of daylight or other full-spectrum light early in the day is essential. Getting outdoors very soon after waking can bring great benefits and preclude the necessity for any other sleep aid.

Note, however, that the bright light of ordinary light bulbs is not sufficient to help the brain regulate melatonin. Even very well lighted rooms give only about 1% of the light that being outdoors in the daylight gives.

To the brain even a well lighted room is like staying in cave. Too much indoor living can ruin energy levels and the ability to get good sleep.

Vigorous exercise and plenty of early daily exposure to daylight both go a long, long way to promoting good sleep, good energy levels and reducing the need for any artificial sleep aid. It's always best to just give one's body what it really needs (once one knows what that is, of course).


The Daily Sleep Pressure Cycle

The third factor can bring one in (or out) of harmony with the daily sleep/wake cycle is sleep pressure. This simply means how long it's been since one last slept. The longer it's been, the greater the pressure to sleep.

What does this mean for curing insomnia? It means no long naps. A short nap is fine, beneficial even, to energy levels and the ability to get good sleep at night.

A daily nap should be kept under thirty minutes, though. Any longer, then when it's time to go to bed one simply will not be tired because they have not gone long enough without sleep.

1 comment:

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