Getting enough sleep is essential for health… Yet, The French are sleeping less and lessLack of sleep increases the risk to develop several chronic diseases, such as cardiovascular disease and cancer. But its most marked impact is visible on the brain, where it directly affects neuronsThis could lead to cognitive impairment. This link between lack of sleep and cognitive decline has just been confirmed by a study from the Mayo Clinic, a medical research institute in Minnesota, USA. Published on September 10, 2025 in the journal NeurologyIt shows that people with sleep disorders have a higher risk of developing dementia.
Chronic insomnia may affect cognition
The study followed 2,750 seniors (average age 70, half of whom were women) for nearly six years. Their common characteristic was that they presented no cognitive impairment at the start of the study. The aim was to assess their cognition throughout the study and compare how it changed in participants with chronic insomnia (approximately 16% of them) compared to those without sleep problems. Each year, participants underwent cognitive tests as well as brain imaging scans, particularly to detect markers characteristic of the condition. Alzheimer's disease, such as the accumulation of amyloid plaques.
During follow-up, 14 of the participants with insomnia developed cognitive impairment, compared to 10 of those without sleep problems. Thus, insomnia was associated with cognitive decline, particularly affecting memory, as well as a higher risk of developing amyloid plaques and brain lesions. "Insomnia doesn't just affect our mood the next day; it could also have an impact on brain health.""That sums it up," says Diego Z. Carvalho, author of the study. We have seen a more rapid cognitive decline and changes in the brain that suggest chronic insomnia could be an early warning sign or even contribute to the emergence of cognitive disorders.
Lack of sleep could accelerate brain aging
These increased risks were linked to sleeping less, not just to having trouble falling asleep. In other words, participants who had difficulty falling asleep but then managed to get enough sleep (by delaying their wake-up time) were not affected as much as those who spent less time asleep. The impact on the latter group's cognition was so significant that they performed on cognitive tests as if they were four years older.
Their poor performance was comparable only to that of participants without insomnia but carrying the APOE4 gene, known to increase the risk of developing Alzheimer's disease. Unsurprisingly, cognitive decline was even more pronounced in insomniac participants carrying this gene. These results highlight the importance of treating chronic insomnia, not only to improve sleep quality, but also to protect brain health during aging., concludes Diego Z. Carvalho. Sleep is not just about rest; it is also essential for good brain health.
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