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Are you the type of person who is most awake after everyone is
asleep for the night or do you find yourself ready for your daily
jog at 5:30 a.m.? While most people are programmed to be productive
during the day and sleep at night, it has been discovered that some
people have a definite morning or evening preference. Researchers
found there is a wide range of morning people and night people,
with most people falling somewhere in the middle of the spectrum.
Researchers have used the labels "larks" to describe
morning people and "owls" to describe night people. These
two types of people were found to have different body clocks that
controlled sleep-wake patterns by adjusting the body temperature
and hormones like melatonin and cortisol.
Studies found that in the majority of people, melatonin levels
rose just before bedtime and fell just after waking up. Also, the
stress hormone, cortisol reached its highest point prior to waking
up and the body temperature reached the lowest point at the mid-point
of a night’s sleep. For example, hormonal fluctuations and
temperature rhythms in larks occurred earlier than they did for
most people, resulting in better performance levels in the morning
and noted tiredness in the early evening hours.
Sleep researchers believed there is a genetic explanation for a
morning or evening preference, however this theory has not yet been
found. Other researchers pointed out that social and biological
factors could play a part in determining a person’s preference.
An example of this could be seen in the temporary night owl habits
of college students, who stay up till the early hours of the morning
cramming for tests and dealing with social pressures. On the other
side of the spectrum, other people adapt to lark-like schedules
because they have a two-hour commute to work each day.
Studies have shown that although many people could go back to their
old schedules, some of the sleep patterns and habits they developed
may be hard to break.
One of the most significant findings shown to affect circadian
rhythms was light.
People with extreme preferences were categorized as having sleep
disorders. Extreme morningness is called advanced sleep phase syndrome
(ASPS) and extreme eveningness is known as delayed sleep phase syndrome
(DSPS). Studies showed that older people had the tendency to develop
ASPS, possibly due to frequent napping during the day and inability
to filter out sensory factors such as light and noise.
ABC
News April 15, 2004
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