Être insomniaque exposerait à davantage de troubles de la mémoire


According to a Canadian study of 28,000 people, lack of sleep caused by chronic insomnia can negatively impact memory.


Forgetting to feed your pet, taking the wrong bus, letting a cake overcook in the oven... Everyone has already noticed: after a bad night, the smallest task becomes more difficult. And when sleep disorders take hold for good, as is the case for 10% in the population suffering frominsomnia, it’s the memory that takes a hit. Researchers from Concordia University in Montreal (Canada) have in fact shown that people suffering from chronic insomnia are more prone to memory problems than those who sleep like crazy. Their study was published May 16 in the medical journal Sleep.


A study of 28,000 people


The researchers recruited 28,000 volunteers over the age of 45, then divided them into 3 groups based on the quality of their sleep. The first included patients suffering from chronic insomnia, the second people with occasional insomnia and the last group brought together people without any sleep problems. Insomnia is said to be chronic if it occurs more than three nights a week for at least three months and it affects the quality of life (fatigue, drowsiness, irritability, difficulty concentrating).


“The group with chronic insomnia performed worse on the tests than individuals in the other two groups.”

Professor Thien Thanh Dang-Vu, researcher in cognitive health and neuroscience and co-author of the study


Subsequently, participants completed a questionnaire and took neuropsychological tests. Result? “The group suffering from chronic insomnia performed less well on the tests than individuals in the other two groups,” said Professor Thien Thanh Dang-Vu, researcher in cognitive health and neuroscience and co-author of the study, in a press release. When performing the task of remembering a list of 15 words, participants with insomnia remembered 3.18 words out of 15 after 30 minutes, compared to 3.42 for participants without a sleep disorder. A difference which seems small but which the authors consider significant. If memory capacities were similar between the groups, this figure should only fluctuate by a few hundredths of a unit at most. However, because each cognitive test was only performed once per person, these results should be approached with caution.


Insomnia is not the only cause of cognitive disorders


Could this drop in performance be due to something other than insomnia? The question is worth asking because memory can be affected by many factors: a stroke, certain medications, alcoholism, etc. To ensure that insomnia was the cause, the authors did not include people diagnosed with dementia or significant head trauma, but they also took into account the possible effects of other problems. health issues such as anxiety and chronic pain.


“The type of memory mainly affected is declarative memory, that is to say the memory of objects and events,” explains Professor Dang-Vu. This memory allows you, for example, to remember the date you obtained your driving license, the place where you met friends, etc. Surprisingly, the group of occasional insomniacs performed better on tests of mental flexibility (ability to switch from one cognitive task to another) compared to the other two groups. A fragile result that researchers explain by hyperactivity resulting from lack of sleep.


Sleep helps optimize memory: when we sleep, the brain sorts information and stores it.


This is not the only unexpected result: the study shows that it was the youngest participants (45 – 65 years old) who most often suffered from insomnia and memory problems. However, we would have expected that the elderly, who are more at risk of dementia, would be the most affected. Could this then be a harbinger of a cognitive decline to come? Can these cognitive deficits be prevented or even reversed? “These are important questions that still need to be explored and will have a major impact on the prevention and treatment of age-related cognitive disorders,” says Professor Dang-Vu.


We know that sleep optimizes memory: when we sleep, the brain sorts information and stores it. Not only does it work on remembering the important bits, it eliminates the ones that aren't. Depending on the phases of sleep, it is not the same memory that comes into play. It is the phases of light and deep sleep that act on declarative memory, precisely the one affected in the insomniac participants in the Canadian study. It remains to be seen whether this impact of insomnia is transient or lasting, and whether it constitutes a predictive sign of the onset of dementia.


Source, health le figaro, May 20, 2019