This new study therefore adds weight to such findings. Previous studies have also found a link between over-sleep and cognitive performance, but most relied upon participants self-reporting how long they sleep nightly – which means the data is less accurate than using an EEG to measure brain activity. Experimental evidence even supports this – showing that even just one night of sleep deprivation temporarily increases beta-amyloid levels in the brain of healthy people.īut it’s less clear why long sleep is linked with cognitive decline. So interfering with sleep might interfere with our brain’s ability to get rid of these. Some of these proteins – like beta-amyloid and tau – are thought to cause dementia.
One theory is that sleep helps our brain flush out harmful proteins that build up during the day. Researchers don’t know for certain why lack of sleep is linked to cognitive decline. Other research has shown that people who have short sleeping times have higher levels of beta-amyloid in their brain – which is commonly found in the brains of people who have Alzheimer’s disease. For example, one study showed that people who reported sleep disturbances, such as insomnia or excessive daytime sleepiness, have a greater risk of developing dementia compared to people who don’t. We know from previous research that lack of sleep is linked to cognitive decline. Interestingly, the impact of sleep duration on cognitive function was similar to the effect of age, which is the greatest risk factor for developing cognitive decline. Overall, the researchers found that sleeping less than 4.5 hours and more than 6.5 hours a night – alongside poor quality sleep – was associated with cognitive decline over time. The researchers also took into account other factors that can affect cognitive decline – including age, genetics and whether a person had signs of the proteins beta-amyloid or tau, which are both linked to dementia. This means that when sleep is tracked from the second night onwards it’s a good representation of a person’s normal sleep habits. While using an EEG to measure brain activity may be somewhat disruptive to sleep on the first night, as people get used to the equipment, sleep tends to return to normal the following night. wideonet/ ShutterstockĪlthough sleep was only measured at one period during the study, this still gave the research team a good indication of participants’ normal sleep habits. Participants would have worn a device similar to this to track their sleep. 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. This was done once, three years after people first completed their annual cognitive tests. Sleep was measured using a single-electrode encephalography (EEG) device, which participants wore on their forehead while sleeping, for a total of between four to six nights. The higher the score, the better their cognition was over time. Their scores from these tests were then combined into a single score, called the Preclinical Alzheimer Cognitive Composite (PACC) score. Throughout the study, participants were asked to complete a range of commonplace cognitive and neuropsychological tests to look for signs of cognitive decline or dementia. At the time of their study, 88 people did not show any 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).
To do this, they looked at 100 older adults in their mid-to-late-70s on average, and tracked them for between four and five years.
The research team wanted to know how much sleep was linked to cognitive impairment over time. Researchers from the Washington University School of Medicine have published a paper that indicates that just like getting too little sleep, sleeping too much may also be linked with cognitive decline. You can listen to more articles from The Conversation, narrated by Noa, here.īut more isn’t always better, as one recent study found. It’s also been shown that not getting enough sleep is linked to cognitive decline and conditions such as Alzheimer’s disease. It helps our body repair itself and function as it should, and is linked to better mental health and lower risk of many health conditions – including heart disease and diabetes. A good night’s sleep is important for many reasons.
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