Sleeping more than 6.5 hours may cause mental decline

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a good night’s sleep is important For many reasons. It helps our bodies repair and function on their own, and it has been linked to better mental health and a lower risk of many Health Conditionsincluding heart disease and diabetes. It has also been shown that not getting enough sleep is associated with cognitive decline and conditions like Alzheimer’s disease,

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But more is not always better, as a Recent study found, Researchers from Washington University School of Medicine have published a paper that suggests that just like getting too little sleep, sleeping too much may also be linked to cognitive decline.

The research team wanted to know how much sleep was associated with cognitive impairment over time. To do this, they looked at an average of 100 older adults in their mid-70s to early 70s, and tracked them between four and five years. At the time of their study, 88 people showed no signs of dementia, while 12 people showed signs of cognitive impairment (one with mild dementia and 11 with a pre-dementia stage of mild cognitive impairment).


Throughout the study, participants were asked to complete a series of general cognitive and neuropsychological tests to look for signs of cognitive decline or dementia. Their scores from these tests were combined into a single figure called the Preclinical Alzheimer’s Cognitive Composite (PACC) score. The higher the number, the better their cognition over time.

Sleep was measured using a single-electrode encephalography (EEG) device, which participants wore on their foreheads for four to six nights while they slept. This was done once three years after people had completed their annual cognitive test. This EEG allowed the researchers to accurately measure brain activity, which would tell them whether someone was sleeping and for how long, and how restful that sleep was.

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Although sleep was only measured over one period during the study, it still provided a good indication of the participants’ general sleep habits. Can be somewhat disruptive to sleep when EEG is used to measure brain activity First Night, As people get used to the device, sleep returns to normal the next night. This means that when sleep is tracked from the second night, it is a good representation of a person’s normal sleep habits.

The researchers took into account other factors that may influence cognitive decline — including age, genetics and whether a person had symptoms of the protein. beta-amyloid or tau, both of which have been linked to dementia.

Overall, the researchers found that sleeping less than 4.5 hours a night and more than 6.5 hours a night — along with poor quality sleep — was associated with cognitive decline over time. Interestingly, the effect of sleep duration on cognitive function was similar to the effect of age, which is the biggest risk factor for the development of cognitive decline.

a good night’s sleep

It may be the case that it is not necessarily the length of sleep that matters, but the quality of that sleep when it comes to the risk of developing dementia.

We know from previous research that sleep deprivation is associated with cognitive decline. For example, one study showed that people who reported sleep disturbances, such as insomnia or excessive daytime sleepiness, had a greater risk develop dementia compared to those who do not. Other research has shown that people who have less sleep time are more likely to high levels of beta-amyloid In their brain – which is usually found in the brains of people who have Alzheimer’s disease.

Researchers don’t know for sure why sleep deprivation is associated with cognitive decline. One theory is that sleep helps our brain flush out harmful proteins that build up during the day. Some of these proteins – such as beta-amyloid and tau – are known to cause dementia. So disrupting sleep can hinder our brain’s ability to get rid of them. Experimental evidence also supports this – showing that even justified a night of sleep deprivation Temporarily increases beta-amyloid levels in the brains of healthy people.

But it is less clear why longer periods of sleep are linked to cognitive decline. previous studies A link has also been found between more sleep and cognitive performance, but most rely on participants self-reporting how long they slept through the night – meaning data from using EEGs to measure brain activity. is less accurate. The new study therefore adds weight to such findings.

What is surprising about this research is that optimal sleep duration is much shorter than previous studies that have been problematic. The study showed that sleeping more than 6.5 hours was associated with cognitive decline over time – which is low when we consider that older adults are advised to sleep in between seven and eight hours from sleep every night.

It may be the case that it is not necessarily the length of sleep that matters, but the quality of that sleep when it comes to the risk of developing dementia. For example, this study also showed that short “slow-wave” sleep – restorative sleep – specifically affected cognitive impairment.

We also cannot tell from this study whether longer sleep duration can independently predict cognitive decline. Essentially, we cannot rule out that participants who slept more than 6.5 hours each night may not have already had brain changes suggestive of dementia that were not taken into account in the trials. . And although the researchers were careful to adjust for factors related to dementia, prolonged sleepers may have other conditions that may have contributed to their cognitive decline that were not taken into account. For example, this may include poor health, socioeconomic status or physical activity level. All of these together may explain why long sleep was linked to cognitive decline.

There are many factors that can affect both the quality of our sleep and whether we experience cognitive decline. Although some factors cannot be prevented (such as genetic predisposition), there are many things we can do to help reduce our chances of developing dementia along with getting a good night’s sleep, such as exercising. and eating a healthy diet. But while the researchers in this study suggested that there is an optimal period of sleep—between 4.5 and 6.5 hours each night—the occasional weekend let-in is unlikely to do any damage to your brain.

Greg Elder is Senior Lecturer in Psychology and Associate Director at Northumbria Sleep Research, Northumbria University, Newcastle. This article first appeared on Conversation,


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