By Dr. Robert Oexman, Director of the Sleep To Live Institute
It wasn’t until the latter half of the 20th century that scientists started to take a real interest in sleep from a neurological perspective and not until the late 1980’s that sleep medicine was recognized as a specialty by the American Medical Association (AMA). In this time, we have learned a lot about various aspects of human sleep cycles and the stages that make up our sleep. There is still much to learn as we take this new medical discipline into the 21st century.
So, what do we know thus far? Sleep is a function of the human body as essential as breathing. It is a complex process that changes to fit our needs throughout our life; babies will spend most of the day sleeping and in a proportion of sleep stages completely different from an adult. Similarly, the elderly will tend to sleep less and with varying amounts of sleep stages than those seen in younger adults.
The sleep and wake cycle that we move through every day is mediated by a process called the circadian rhythm. This process picks up cues (called zeitgebers) from external stimuli, of which the primary one is daylight. The zeitgebers move the circadian rhythm through phases on a roughly 24-hour schedule. The phases are marked by hormone releases such as melatonin and core body temperature changes.