Insomnia and sleep cycles
‘Insomnia is defined as ‘a perception of inadequate sleep. Normal sleep varies from 4-11 hrs, and one person’s insomnia is another’s normal sleep pattern. In normal sleep, brain electrical waves cycle though initial drowsy awareness into ‘sleep spindles’ where patterns cycle through four progressively deeper states, resulting in deep restorative sleep, into rapid eye movement (REM) sleep with dreaming, then back into non-REM cycles. Disruption of any of these stages can cause insomnia, resulting in fatigue, loss of concentration, tension headaches and irritability (Neikrug, 2010).
•Stress. Major life changes such as the death or illness of a loved one, divorce or a job loss, as well as chronic stress due to overwork or relationship problems.
•Anxiety. Agitation and restlessness typically accompany anxiety, with constant fear about what might happen or what people think of you. Excessive about not being able to sleep well and trying too hard to fall asleep can also cause insomnia
•Depression. Typically leads to an inability to respond to normal stimuli. Chemical imbalances can disrupt sleep patterns, leading to too much sleep or insomnia.
•Medications. Many prescription drugs can interfere with sleep, including some antidepressants, heart and blood pressure medications, allergy medications, stimulants (such as Ritalin) and corticosteroids.
•Caffeine, nicotine and alcohol. Coffee, tea, cola and other caffeine-containing drinks are well-known stimulants. Drinking coffee in the late afternoon and later can keep you from falling asleep at night. Alcohol is a sedative that may help you fall asleep, but it prevents deeper stages of sleep
•Medical conditions. Conditions linked with insomnia include arthritis, cancer, heart failure, lung disease, gastroesophageal reflux disease (GERD), overactive thyroid, stroke, Parkinson disease and Alzheimer's disease.
•Change in your environment or work schedule. Travel or working a late or early shift can disrupt your body's circadian rhythms
•Aging. With age, your internal clock often advances, which means you get tired earlier in the evening and wake up earlier in the morning. Sleep apnea and restless legs syndrome become more common with age.
•Hormone shifts such as those that precede menstruation and those during menopause.Changes in levels of cortisol, progesterone in the female cycle, or estrogen during menopause are correlated with increased occurrences of insomnia.
“Recent studies found that disturbed sleep is rare in healthy older adults”. The need for sleep did not change with age, but the ability to get the needed sleep decreased with age. Circadian rhythms, with variations in core body temperature, hormone secretion and the sleep-wake cycle, oscillate approximately every 24 h. As people age, their circadian rhythms become weaker, desynchronized and lose amplitude. Secretion of the hormone melatonin, known to play an important role in the sleep-wake cycle, gradually decreases with age, possibly resulting in reduced sleep efficiency, and the amplitude of the circadian rhythmmay decrease with age (Neikrug, 2010).
Changes in the phasing of the circadian rhythm can cause changes in the timing of the sleep period.
For example, phase advance causes to wake up earlier in the morning and get tired earlier in the evening. Individuals with advanced sleep rhythms will typically fall asleep between 7:00–9:00 pm, correlating with the cyclical drop in body temperature, and wake up about 8 h later between 3: 00–5: 00 am.
Due to societal pressures, many adults with an advanced sleep-wake cycle resist their fatigue and attempt to stay up late, believing that they will wake up later in the morning. Yet these individuals will still wake up early in the morning as a result of their phase advancement. This behaviour results in less total time in bed, less sleep time and daytime sleepiness.
The most effective and common treatment for circadian rhythm shifts is exposure bright light, as bright light is the strongest cue for circadian corrections. Bright light is lacking in winter, hence the worsening of symptoms at this time of year.
People with an advanced sleep-wake cycle should increase exposure to bright light in the early evening and avoid bright light in the morning. Studies have shown that artificial light therapy is effective in both healthy and institutionalized elderly patients.
Neikrug, A.B. and S. Ancoli-Israel, Sleep Disorders in the Older Adult – A Mini-Review. Gerontology, 2010. 56: p. 181–189
“Hibernation is a state of inactivity and metabolic depression in endotherms”. (Endotherms are humans and other mammals that keep their body temperature the same no matter what the climate is like. Their body is regulated through negative feedback.
For example, when our body temperature decreases due to the cold, we shiver to increase the body temperature. When the body temperature increases, we sweat to decrease the body temperature.) http://en.wikipedia.org/wiki/Hibernation“Hibernation is characterized by low body temperature, slow breathing and heart rate, and low metabolic rate. Often associated with cold temperatures, hibernation conserves energy during periods when food is scarce. To achieve this energy saving, an endotherm will first decrease its metabolic rate, which results in decreased body temperature.
Hibernation may last several days, weeks, or months depending on the species, ambient temperature, time of year, and individual animal's body condition.”There are many research projects currently investigating how to achieve "induced hibernation" in humans. Human hibernation would be useful for a number of reasons, such as saving the lives of seriously injured people by temporarily putting them in a state of hibernation until treatment can be given. In addition, hibernation would be useful for humans in the future for interstellar travel. http://en.wikipedia.org/wiki/Hibernation