Published on: November 18, 2015
by Women’s Brain Health Initiative:
Why is sleep so important?
While researchers are still trying to determine exactly why we need sleep, we do know that it is essential for our survival. For example, animal studies have found that when rats are deprived of sleep, their life expectancy falls dramatically from two or three years to only three weeks.
Up until the 1950s, most people believed that sleep was a necessary but passive part of everyday life; a time when the body would shut down and switch off. However, modern research shows that our brains are incredibly active during sleep. At night, we move through five sleep phases that take us from light sleep to deep sleep to rapid eye movement sleep in a continuous cycle, each one lasting 90 to 110 minutes. The amount of sleep your body needs depends on many factors, but most adults seem to require seven or eight hours every night.
Without sleep, our nervous system, heart and immune system couldn’t function properly. According to researchers, our bodies grow and repair cells at a faster rate while sleeping and neurons in the brain reconnect or make new connections, which consolidates memory and improves focus. Recent findings also suggest that sleep helps clean our brains of “garbage.” Not those crazy thoughts but the waste proteins that accumulate during the day, such as
Beta-amyloid is a sticky protein found throughout the body that gradually clumps together into what is known as amyloid plaques. Many researchers believe that high concentrations of amyloid plaques are toxic for nerve cells in the brain, and that these plaques play a key role in the development of Alzheimer’s disease.
Alzheimer’s is generally associated with two types of abnormal protein buildup within the brain’s cerebral cortex: amyloid plaques and neurofibrillary tangles, both of which spread damage from cell to cell by causing neurons to lose their ability to function and communicate efficiently. Though these plaques and tangles do accumulate naturally with age, some scientists believe that they accumulate in greater quantities in people with Alzheimer’s, while others suggest that plaques form in different patterns in those with the disease.
Sleep, Beta-amyloid Proteins and Alzheimer’s
Beta-amyloid buildup is believed to be one of the earliest stages of Alzheimer’s, appearing in the brain between 10 and 20 years before symptoms manifest. Recent findings suggest that there is a close relationship between amyloid plaques and sleep disruption, but as sleep problems are very common in people with Alzheimer’s, scientists are attempting to discover whether poor sleep is a cause or an effect of the disease.
Several large-scale studies support the theory that disrupted sleep is a risk factor for cognitive decline. In 2012, a 15-year study by the University of California, San Francisco, assessing 1,309 elderly women found that after five years, those with nighttime wakefulness were more than twice as likely to show impaired cognitive functioning. They also discovered that women with sleep-disordered breathing, or sleep apnea, were twice as likely to develop mild cognitive impairment or dementia.
Scientists at Washington University in St. Louis have shown in both human and animal subjects that sleep loss contributes to the accumulation of amyloid plaques characteristic of Alzheimer’s. In a study on “cognitively normal” people between 45 and 80 years of age, they found that participants who woke up more than five times per hour were more likely to have amyloid plaque buildup compared to “more efficient” sleepers.
Another study in 2012 by Brigham and Women’s Hospital in Boston followed 15,263 women, aged 70 or older, over a span of six years. The researchers found that those participants who got too little sleep (five hours or less), or even too much sleep (nine hours or more), had lower average cognition, and that consistent abnormal sleep was cognitively equivalent to two years of aging. Here, a normal night’s sleep was considered to be seven hours. This study also found that too much or too little sleep was linked to amyloid plaque buildup – so it’s not necessarily a case of the more sleep the better.
Questions still remain about the relationship between poor sleep and elevated beta-amyloid levels. While many studies suggest that sleep deprivation is a risk factor for the development of amyloid plaques and possibly Alzheimer’s, other research has shown that the accumulation of plaques is associated with wakefulness and may in fact cause sleep disruption. It may be that this relationship is cyclical, where an initial increase in time spent awake leads to the clumping of beta-amyloid, which then leads to further sleep disruption, leading to further plaque buildup, and so on.
University of California Berkeley scientists have found compelling evidence that poor sleep — particularly a deficit of the deep, restorative slumber is a channel through which the beta-amyloid protein believed to trigger Alzheimer’s disease attacks the brain’s long-term memory. “Our findings reveal a new pathway through which Alzheimer’s disease may cause memory decline later in life,” said UC Berkeley neuroscience professor Matthew Walker, senior author of the study published in June 2015 in the journal Nature Neuroscience. While most research in this area has depended on animal subjects, this latest study has the advantage of human subjects.
How Strong is the Link?
Before you panic, it is estimated that up to half of adults have trouble sleeping, and that this in itself isn’t necessarily a sign of Alzheimer’s disease. Many different factors can contribute to a sleepless night, such as age, stress, medications, as well as physical and mental health conditions. However, these findings do undeniably point to the fact that, for most people, getting between seven and eight hours of sleep is good for you, and that if you do experience problems sleeping, you should do your best to address them.
How to sleep better
There are many techniques you can use to achieve a better night’s sleep, including avoiding caffeine and alcohol at least four hours before bed, ensuring that you get regular exercise and receiving as much light exposure as possible during the day, to help your body maintain a strong biological clock.
It is also a good idea to remove sources of distraction or stimulation from the bedroom by banning laptops, phones or tablets, and to avoid watching anything too exciting before bed. Sleep specialists also recommend keeping your clock hidden to prevent you from opening your eyes to check the time, which will wake you up further. Contact your doctor if you are worried about persistent sleep problems. A medical professional will be able to recommend an appropriate treatment for your insomnia.
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