Older adults who sleep less than 4,5 hours or more than 6,5 hours a night are at greater risk for cognitive decline
Don't store avocado like this: it's dangerousOlder adults who sleep less than 4,5 hours or more than 6,5 hours a night are at greater risk for cognitive decline
A good night's sonno it is important for our health for several reasons:
- helps the body repair itself and function as it should
- favors a better mental health
- protects against many health conditions, including heart disease and diabetes.
Not getting enough sleep has also been shown to be linked to cognitive decline and neurodegenerative diseases, such as Alzheimer's disease.
A systematic review
According to one study recent too little sleep may be linked to cognitive decline. The research team aimed to find out how much sleep was linked to cognitive impairment over time. To do this, they surveyed an average of 100 seniors, between the mid to late 70s, and monitored them for four to five years. At the time of their study, 88 people showed no signs of dementia, while 12 showed signs of cognitive impairment (one with mild dementia and 11 with the pre-dementia stage of mild cognitive impairment).
During the study, participants were asked to complete a series of common cognitive and neuropsychological tests, to look for signs of cognitive decline or dementia. The scores from these tests were then combined into a single score, called the Preclinical Alzheimer Cognitive Composite (PACC) score. The higher the score, the better their cognition was over time.
Sleep was measured using a single electrode encephalography device (EEG), which participants wore on their foreheads during sleep, for a total of four to six nights. This EEG allowed the researchers to accurately measure brain activity, which would tell them whether or not someone was asleep (and for how long) and how restful that sleep was.
Although sleep was only measured over a short period of time, this still provided the research team with a good indication of the participants' normal sleep habits. The researchers also considered other factors that can influence cognitive decline, including age, genetics, and whether there were beta-amyloid or tau proteins, both of which are linked to dementia.
We know from previous research that the lack of sleep is linked to cognitive decline. For example, one study has shown that people with sleep disorders, such as insomnia or excessive daytime sleepiness, have a higher risk of developing dementia. Other research have shown that people who get little sleep have higher levels of beta-amyloid in the brain, which is commonly found in the brains of people who have Alzheimer's disease.
Researchers aren't sure why sleep deprivation is linked to cognitive decline. One theory is that sleep helps our brains eliminate harmful proteins, which build up throughout the day. Some of these proteins, such as beta-amyloid and tau, are thought to cause dementia. So interfering with sleep could interfere with our brain's ability to get rid of it. Experimental evidence even shows that even just one night of sleep deprivation could temporarily increase beta-amyloid levels in the brain even in healthy people.
What is surprising about the results of this study is that optimal sleep duration is much shorter than what previous studies have suggested is problematic. The study showed that sleeping longer than 6,5 hours is associated with cognitive decline over time.
It could also be that it's not necessarily the length of sleep that matters, but the quality of that sleep when it comes to the risk of develop dementia. For example, this study showed that having less restful sleep could impact cognitive impairment.
According to the researchers, there would be an optimal sleep duration, ranging between 4,5 and 6,5 hours each night, but the occasional weekend rest is unlikely to damage the brain. Furthermore, although some factors are not predictable (such as genetic predisposition), there are many things we can do for get a good night's sleep and help reduce the likelihood of developing dementia, like getting regular exercise and eating a healthy, balanced diet.
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Photos: Oxford Academic
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