Everyone has a clock inside, though it isn’t digital and it doesn’t have hands that move around the face to indicate the time, as an analog clock does. However, scientists have found that a human being’s biological clock works on a 24-hour cycle, and is sometimes referred to as the circadian rhythm. The term comes from the roots “circa” and “diem” which together mean “round the day.”
This biological process recurs naturally and can be affected by light or the absence of light.It is also subject to slight changes due to body temperature, the lack of proper body fluids and dehydration, among other influences. Medical research and sleep studies indicate that disruption of this process is closely related to sleep disorders and the way the body produces a hormone called melatonin.
Melatonin is made during the night, for the most part. When there is sufficient daylight, the process slows down or stops. Night work can significantly affect the level of this hormone produced in the body. All of this contributes to a person’s ability to sleep. The body will continue to work on the circadian rhythm or body clock if there is not sufficient daylight.
But this absence of light will gradually change, getting a bit faster or a bit slower. Some people find it very difficult to adjust to this schedule. Rotating shift work may be even more difficult, and work performance can reflect this. If a person regularly lives by a wrist watch or the digital clock on a cell phone, rather than by the internal timekeeper, problems can develop. Someone who works at night can often start to see reduction in performance and never really become efficiently active at night.
There is a similar effect when we travel long distances, crossing several times zones. If you fly from New York to a location in eastern Europe, and land at 6 a.m. your body still feels as if it is late the night before, about 11 p.m. It will take a few days for the body to catch up to its natural light/dark rhythm.
Not Dark Enough
While some people seem to be able to sleep anywhere, at any time, there are others who are quite sensitive to the amount of light in their bedroom. If the room is not dark enough they find it difficult to get to sleep. In Alaska and the Northern Territories, people have to put extra covering on windows when the sun stays above the horizon for most of a 24-hour period.
Other factors can make significant changes in sleep patterns, due to chemical changes in the body. Certain illnesses, clinical depression, or a head injury, can seriously disrupt the body clock. Outside influences can also have a negative effect on sleep patterns. Some medications have this as a serious side effect. Alcohol affects some people this way as well.
Some individuals are just fine with going to sleep very late in the day and sleeping well into the morning, even when the sun is up. Others are able to go to sleep early in the evening and wake at 3 a.m., without long-term negative effects. But the majority of people are guided by their internal body clock.