Ahh, the sweet balm that soothes the nerves and restores the soul at the end of the day. Sadly, for some of us it is elusive, and its intangible rewards sporadic. Sleep. It can get interrupted, disrupted and corrupted. Even in its worst state, sleep can be the most desired gift for the time.
There have been thousands of sleep studies over the years, but science still isn’t completely sure why we need it. “Completely” is the key word. One goofy answer is that we sleep to cure sleepiness. It’s agreed that sleep gives the body a chance to rejuvenate. That we know about rapid eye movement sleep (REM) shows that sleep is not a totally static process for the brain. Asleep, it still needs calories. The amount of sleep a person needs is purely singular, and depends on his or her circadian rhythm, which is that twenty-four-hour cycle of biological activities that occur regularly and dependably regardless of illumination. What sleep experts look for are maximum melatonin levels and minimum core body temperature, reporting that one should be asleep at least six hours before lowest temp is achieved. When these occur just after the middle of the sleep cycle, the timing is deemed to be just right (Wyatt, 1999) (Dijk, 2002) (Taillard, 2011).
Too much sleep can be as unhealthy as too little. Where lack of sleep can increase the chance of accidents and CVD issues, a plethora might increase risk of other-cause mortality (Ferrie, 2007). Because animals with brains sleep, we might infer that it’s a needed pastime. Regardless of who and how much, the fact is that we heal better when we sleep, the immune system gets a chance to recoup, memory and cognitive function improve, and a general restoration takes place. And now there’s another reason to cut Z’s…the prevention of Alzheimer’s disease and related cognitive disorders.
Whether it’s more hypothetical than proven, a new study released by the University of Rochester hints that a good night’s sleep can ward off Alzheimer’s disease (Xie, 2013). Lead author, Maiken Nedergaard, notes that sleep serves a vital function, a collective term that includes washing debris out of the brain. The brain produces toxic waste as it works every day. This new study says that while we sleep the brain shrinks in size, allowing the spaces between brain cells to enlarge so that junk can be washed out by the cerebral spinal fluid that is pumped around it (Underwood, 2013).
Researchers in Nedergaard’s lab noticed that mice whose brains were probed while conscious would sometimes fall asleep. When that happened, cerebrospinal fluid would rush into the brain’s interstitial space and wash away cellular debris. Delving into the phenomenon, they observed that the brain’s glial cells, a web of connective tissue that supports neurons, expand during wakefulness to reduce the space between cells and shut off the movement of fluid. During sleep, the interstitial volume changes again.
Interstitial fluid is a solution that bathes the area around cells with a concoction that contains sugars, salts, fatty acids, amino acids, coenzymes, hormones, and neurotransmitters. Different areas of the body have different concentrations of these substances. Little attention was paid to the area between cells before Nedergaard’s investigation because that was considered just space (Herculano-Houzel, 2013). The brain’s drainage system was termed the glymphatic system, a functional waste management setup that removes extracellular proteins and metabolic waste products from the pathway, but reliant upon the glia instead of a dedicated, albeit absent, lymphatic network.
To double-check their findings, scientists injected the mouse brains with proteins that parallel those implicated in Alzheimer’s disease (AD)—the amyloids. These were washed away faster from the brains of sleeping mice than their awake peers. It is the accumulation of these soluble proteins at the synapses that is believed by some to initiate the disease (Tomiyama, 2010) (Esparza, 2013).
Fragmented sleep is that which does not include much slow-wave sleep and is not refreshing. Total time asleep is less than normal, affecting about a third of all adults. Unfragmented-consolidated sleep is divided into two periods with a gap between. This “bi-phasic” sleep is common and is something people can adjust to. Fragmented sleep is characteristic of Alzheimer’s and Parkinson’s patients, though it is common to the aging process. However, there is debate about whether increased fragmentation is a normal part of aging or indicative of an underlying pathology. Regardless, it is associated with cognitive performance (Lim, 2013). In any case, it’s unpleasant to experience the next day’s sleepiness. There are pharmaceutical sleep aids, but the natural ones, such as valerian and melatonin, are safer.
Melatonin is produced in the brain, but decreases with age and in those with Alzheimer’s disease. There are data from clinical trials demonstrating that melatonin can slow the progression of cognitive impairment in AD patients by protecting neural cells from amyloid-mediated toxicity and by arresting the formation of plaques in the first place (Lin, 2013). As a noted anti-oxidant, melatonin is able to scavenge the free radicals that are likewise implicated in AD etiology (He, 2010), and to improve mitochondrial energy metabolism (Cheng, 2006) (Liu, 2013). Produced in the pineal gland from tryptophan, melatonin, as a sleep aid, lowers body temperature and blood pressure, a condition required for sound sleep.
If sleep can clear the abnormal accumulation of neurotoxins (Rothman, 2012), and if melatonin can help resolve dysfunctional sleep patterns, then this bag of ideas might just hold more than water.
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