6 May 2013

Sleep well

Sleep and dream well

 is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It
is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than being in hibernation or a coma. Sleep is a heightened
anabolic state, accentuating the growth and rejuvenation of the immune, nervous, skeletal and muscular systems. It is observed in all mammals, all birds, and many reptiles,
amphibians, and fish.
Sleep timing is controlled by the circadian clock, sleep-wake homeostasis, and in humans, within certain bounds, willed behavior. The circadian clock—an inner
timekeeping, temperature-fluctuating, enzyme-controlling device—works in tandem with adenosine, a neurotransmitter that inhibits many of the bodily processes associated
with wakefulness. Adenosine is created over the course of the day; high levels of adenosine lead to sleepiness.
The optimal amount of sleep is not a meaningful concept unless the timing of that sleep is seen in relation to an individual's circadian rhythms. A person's major sleep
episode is relatively inefficient and inadequate when it occurs at the "wrong" time of day; one should be asleep at least six hours before the lowest body temperature. The
timing is correct when the following two circadian markers occur after the middle of the sleep episode and before awakening: maximum concentration of the hormone
melatonin, and minimum core body temperature.
Human sleep needs can vary by age and among individuals, and sleep is considered to be adequate when there is no daytime sleepiness or dysfunction. Moreover,
self-reported sleep duration is only moderately correlated with actual sleep time as measured by actigraphy, and those affected with sleep state misperception may typically
report having slept only four hours despite having slept a full eight hours.
Researchers at the University of Warwick and University College London have found that lack of sleep can more than double the risk of death from cardiovascular disease,
but that too much sleep can also be associated with a doubling of the risk of death, though not primarily from cardiovascular disease.[34][35] Professor Francesco
Cappuccio said, "Short sleep has been shown to be a risk factor for weight gain, hypertension, and Type 2 diabetes, sometimes leading to mortality; but in contrast to the
short sleep-mortality association, it appears that no potential mechanisms by which long sleep could be associated with increased mortality have yet been investigated.
Some candidate causes for this include depression, low socioeconomic status, and cancer-related fatigue... In terms of prevention, our findings indicate that consistently
sleeping around seven hours per night is optimal for health, and a sustained reduction may predispose to ill health."
Furthermore, sleep difficulties are closely associated with psychiatric disorders such as depression, alcoholism, and bipolar disorder. Up to 90% of adults with depression
are found to have sleep difficulties. Dysregulation found on EEG includes disturbances in sleep continuity, decreased delta sleep and altered REM patterns with regard to
latency, distribution across the night and density of eye movements.
Children need more sleep per day in order to develop and function properly: up to 18 hours for newborn babies, with a declining rate as a child ages. A newborn baby spends
almost 9 hours a day in REM sleep. By the age of five or so, only slightly over two hours is spent in REM. Studies say that school age children need about 10 to 11 hours of
sleep.
The siesta habit has recently been associated with a 37% reduction in coronary mortality, possibly due to reduced cardiovascular stress mediated by daytime sleep.
Nevertheless, epidemiological studies on the relations between cardiovascular health and siestas have led to conflicting conclusions, possibly because of poor control of
moderator variables, such as physical activity. It is possible that people who take siestas have different physical activity habits, e.g., waking earlier and scheduling more
activity during the morning. Such differences in physical activity may mediate different 24-hour profiles in cardiovascular function. Even if such effects of physical activity can
be discounted for explaining the relationship between siestas and cardiovascular health, it is still unknown whether it is the daytime nap itself, a supine posture, or the
expectancy of a nap that is the most important factor.
Please not forget for take your rest and sleep well!


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