Multiple theories exist as to why humans sleep. However, the exact reason is not well understood.
Inactivity Theory-suggests that inactivity at night is an adaptation that served a survival function by keeping organisms out of harm’s way at times when they would be particularly vulnerable
Energy Conservation Theory-suggests that the primary function of sleep is to reduce an individual’s energy demand and expenditure during part of the day or night. Energy metabolism is significantly reduced during sleep (by as much as 10% in humans and even more in other species).
Restorative Theories-suggests sleep provides an opportunity for the body to repair and rejuvenate itself. Many of the major restorative functions in the body like muscle growth, tissue repair, protein synthesis, and growth hormone release occur mostly, or in some cases only, during sleep. Other rejuvenating aspects of sleep are specific to the brain and cognitive function.
Brain Plasticity Theory-suggests sleep is correlated to changes in the structure and organization of the brain. For example, that sleep plays a critical role in brain development in infants and young children. Infants spend about 13 to 14 hours per day sleeping, and about half of that time is spent in REM sleep, the stage in which most dreams occur. This is also seen in adults as the effect that sleep and sleep deprivation have on people’s ability to learn and perform a variety of tasks.
Many individuals do not realize that a lack of sleep, especially on a regular basis, is associated with long-term health consequences. Poor sleep is associated with lower life expectancy. Hublin et al (2007) concluded that five hours or less per night increased mortality risk from all causes by roughly 15%. Furthermore, research also shows that habitually sleeping more than nine hours is also associated with poor health conditions including:
There are many internal and external factors that can affect the quantity and quality of the sleep we obtain. These can include changes in the structure and function of the brain during development, stress and medical conditions, especially those that cause chronic pain or other discomforts. External factors, such as what we eat and drink, the medications we take, and the environment in which we sleep can also greatly affect sleep. In general, all of these factors tend to increase the number of awakenings and limit the depth of sleep.
The division of sleep medicine from Harvard medical school (2007) suggests the following simple and natural sleep promotion techniques may improve ones sleep hygiene.
Follow through with these suggestions. Maintaining consistency increases the chances of achieving restful sleep. It is important to realize that all sleep problems are not easily treated and could signify the presence of a sleep disorder such as apnea, restless legs syndrome, narcolepsy, or another clinical sleep problem. If a patients’ sleep difficulties don’t improve through good sleep hygiene, referral to a medical doctor or sleep specialist is warranted.