It’s no secret that getting too little sleep is bad for your mental faculties. In past studies, it’s been proven that sleeping too little can cause a person to end up with conditions such as Alzheimer’s disease and other cognitive issues later on in life.
But a new study conducted by researchers from the Washington University School of Medicine shows that getting too much sleep can result in a person experiencing the same cognitive decline as someone getting too little sleep.
For their study, the team aimed to understand just how much sleep was linked to cognitive decline over time, and studied 100 elderly adults in their mid-to-late 70s over a length of between four to five years.
The studies conducted on the participants involved numerous cognitive and neuropsychological tests meant to identify signs of cognitive decline. The individual scores on the tests were then combined into a single score called the Preclinical Alzheimer Cognitive Composite (PACC) score, in which a higher score signified better cognitive function over time.
Combined with these tests, the team also monitored the amounts of sleep participants got using a single-electrode encephalography (EEG) device planted on their foreheads. This sleep measurement activity was done once on each participant for between four to six nights after they’d completed their yearly cognitive tests over three years.
After taking into account all factors, including age, genetics, and the presence of proteins linked to the development of dementia, the team concluded that sleeping less than 4.5 hours, and more than 6.5 hours a night – poor sleep included – had associations with mental and cognitive decline over time.
How much to sleep, then?
This conclusion comes as a bit puzzling considering the advice generally given to us – to get between seven and eight hours of sleep each night.
With the study showing that sleeping over 6.5 hours per night can be associated with cognitive decline, the next step is to ascertain just how closely linked this association is in terms of cause and effect.
It could be the case in this study (as well as other similar, previous studies) that individuals sleeping longer than 6.5 hours per night may have already had pre-existing cognitive decline conditions that weren’t pinpointed during tests.
Then there are also other factors such as physical activity levels, financial situations, social relationships, and others that could cause cognitive decline on an individual level.
Overall, how the amount of sleep – be it too much or too little – affects a person’s cognitive mental functions is still very much a mystery, and there’s still plenty more to uncover before we can safely determine how much sleep is truly optimal for preserving our mental faculties.
But regardless of the results, it’s still worth keeping tabs on your own sleep patterns to ensure that you’re getting enough quality rest during the night – which is probably the most important objective when going to bed anyway.
In the end, it’s all based on your needs and preferences. If you feel as if you need more sleep than you’re currently getting, staying in bed for a little longer probably won’t be such a bad thing. And if you feel your sleep patterns getting disrupted due to any number of factors (insomnia, medications, environmental causes), do yourself a favor to get them fixed.
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Cover image sourced from Live Japan and Kemin Industries. For illustration purposes only.
