These days we are less inclined to regulate our activities based around daylight. More and more people work late into the night and sometimes all night, every night. Our body clock can’t work out what’s going on.
Our bodies are tuned to a 24 hour cycle of sleep and waking. Perhaps not surprisingly we refer to this as our body clock. The body clock is regulated by a tiny cluster of cells known as the suprachiasmatic nuclei, located in the hypothalamus region of the brain. During the 24 hour cycle a whole series of changes takes place within hormones and the endocrine system. Light and darkness affects our bodies too. Light has the effect of turning on systems relating to the hormone melatonin and darkness has the effect of releasing melatonin into the bloodstream and this has the effect of reducing body temperature.
These days we are less inclined to regulate our activities based around daylight. More and more people work late into the night and sometimes all night, every night. Our body clock can’t work out what’s going on. It has no concept of shift work, being on-call, changes in time zones or why food and drink is being consumed any time of day or night. It remains the case that we simply don’t know how the delicate and complex relationship between sleep and health actually works beyond some of the more obvious short-term effects.
Rotating shifts have been linked to coronary heart disease (CHD), lifestyle disruptions, anxiety, and a variety of gastric disturbances. Twelve hour rotating shifts that involve heavy manual work seem to be the most harmful to health. Daytime sleep never seems to fully compensate as this is typically more fragmented and shorter than it would be at night.
The body clock can desynchronize for various reasons. Apart from light exposure other environmental factors such as physical activity and food intake act as daily cues to help maintain the body clock. Our age and our lifestyle can also contribute to body clock disruption. As people get older the part of the brain that helps to regulate the body clock starts to deteriorate. This, for example, can lead to increases in body temperature during the night and disturbed sleep. Older people tend to rely much more on external cues to monitor their sleep-wake cycle.
Anything that affects the central nervous system (CNS) has to be taken into consideration. Typically includes caffeine, nicotine and alcohol. A coffee just before bedtime can significantly delay the onset of sleep. As caffeine is found in many drinks and foods (including chocolate), late eating can be another factor in disrupted sleep.
Tuning your body clock means working with rather than against it. The body clock is a flexible instrument but it doesn’t like too much abuse or disruption.