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Does Sleeping Over 6.5 Hours Per Day Cause Cognitive Decline? Study Finds Out

Sleeping for less than 4.5 hours, or more than 6.5 hours can lead to cognitive decline, as per a study

Written by: Shubhangi ShahPublished at: Nov 26,2021
Updated at: Nov 26,2021

Getting a good night’s sleep is extremely important for overall health. Firstly, it allows your brain to relax and recharge. It improves your concentration and decreases your chance of getting heart disease and stroke. When you sleep poorly, you get at a greater risk of type-2 diabetes, mental health ailments, and your overall quality of life gets affected. These are the health impacts of undersleeping. But what about oversleeping? Does it have harmful health impacts too? As per a study undertaken by researchers in the United States, sleeping for more than 6.5 hours per night can lead to cognitive decline.

About The Study

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The study was undertaken by researchers from the Washington University School of Medicine, who wanted to know how much sleep leads to cognitive decline. The study was published in the Brain Journal, which is published by Oxford University Press.

  • The study involved 100 participants, who were all older adults in their mid-to-late seventies.
  • They studied over a course of four to five years.
  • During the time the study was undertaken, 88 participants showed signs of dementia, in which the person’s ability to think, remember, and make decisions gets impaired. Understandably, it impacts the person’s day-to-day life. 
  • The remaining 12 participants showed signs of cognitive impairment in which one had mild dementia, and the rest were at the pre-dementia stage of mild cognitive impairment.

How Was The Study Undertaken & Its Results?

This is how the study was undertaken:

  • The participants undertook a range of commonplace cognitive and neuropsychological tests. This was done to look for signs of dementia and cognitive decline.
  • The scores of the various tests were then combined into one called the Preclinical Alzheimer Cognitive Composite (PACC) score.
  • Those who scored higher, which means had a better PACC score showed a better cognitive performance. This is how cognitive performance was measured.
  • For studying sleep, the participants wore a single-electrode encephalography (EEG) device on their forehead. The device allowed the researchers to track brain activity, which means they were able to track if someone was asleep or not as well as its quality, i.e. how restful it was. 
  • This was measured for four to six nights. Throughout the course of the study, this was done once, three years after the participants first undertook the cognitive tests. 
  • Other factors, such as age, genetics, etc, were also taken into account when measuring the participants’ cognitive performance.

Sleeping for less than 4.5 hours per night, or more than 6.5 hours a night along with the poor quality of sleep leads to cognitive decline, the study found out. Another interesting result was that the impact of sleep duration on cognitive performance was similar to that of age, and age is a major risk factor in the case of dementia. Hence, this study clearly shows that both under, as well as oversleeping, are bad as far as cognitive performance is concerned. 

Also read: Not Just Typical 8 Hours Sleep, Here Are 7 Kinds Of Rest Every Person Needs

Importance Of Sleep

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According to the Sleep Foundation, every adult should get at least seven to nine hours of sleep daily. This duration is more or less depending on age. The importance of sleep includes:

  • Qualitative and the right amount of sleep is crucial for sound cognitive and behavioral functions. On the other hand, lack of sleep can lead to frequent mood swings, poor concentration, delayed reactions, and reduced cognition, as per the Sleep Foundation. 
  • They are also at a higher risk of several serious health issues, which include cardiovascular diseases, type-2 diabetes, obesity, hypertension, and poor mental health.
Also read: Can Excessive Sleeping Increase Risk Of Stroke? Know From Expert

How To Sleep Better?

As you already saw, the right amount of as well as qualitative sleep is extremely crucial for good health. And to get that, you should inculcate healthy sleep practices, such as:

  • Set a specific bedtime, which means go to sleep and wake up at the set time, even on weekends, the Sleep Foundation recommends.
  • Maintain a temperature that is comfortable for you. A room that is too cold or too hot can disrupt sleep.
  • Equally important is light. Hence, make sure your room is dark enough to aid sleep.
  • Avoid being in front of the screen, whether it is your smartphone, laptop, or TV, for a few hours before going to bed.
  • Avoid stimulants such as caffeine or alcohol right before your bedtime. The same goes for tobacco. 
  • Similarly, avoid larger meals close to your time to sleep.
  • Mattress, bedsheet, and pillow are very important, hence, ensure these are comfortable enough to get you a good night’s sleep.
  • Also exercising daily and getting exposed to ample sunshine are also good for qualitative sleep. 

Hence, as you can see, sleep has an association with your cognitive performance. Hence, make sure you get enough and a good quality sleep every night. However, remember that both under and oversleeping are detrimental, hence, try to avoid that. 

Photo Credit: Unsplash


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