How many hours do you sleep at night? A sleep time that does not exceed six hours is associated with an increased risk of dementia, according to a study conducted jointly by researchers from Inserm, the University of Paris and University College London (UCL). They publish their results on April 20, 2021 in the scientific journal Nature Communications.

Nearly 8,000 participants followed for 30 years

This study looked at the health of 7,959 Britons since 1985. All participants self-reported their sleep duration six times between 1985 (age range: 35 to 55) and 2015 (range age: 63 to 86). Information that allowed researchers to extract data on sleep duration at 50, 60, and 70 years for each participant.

In 2012, around 3,900 of them also wore an accelerometer watch, which captures movements at night, in order to verify the accuracy of their estimates.

At the same time, the researchers recorded the diagnoses of dementia, including Alzheimer’s disease, until March 2019.

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Up to 40% more dementia

The result: The risk of dementia is 20-40% higher in participants who get little sleep – six hours a night or less – at the age of 50 or 60 compared to those who get seven hours of sleep.

Another observation is that people aged 50 to 70 who consistently had a short sleep period had a 30% increased risk of dementia, regardless of their possible health problems.

No cause and effect

In summary, “these results suggest that midlife sleep may play a role in brain health“note theInserm in a press release.

But beware. If a link seems to exist between sleep time and the risk of dementia, the researchers remain cautious: they have not yet demonstrated a cause and effect relationship between these two factors.

Prevent or delay dementia

However, this study provides new evidence that sleep habits, before the onset of dementia, are likely to contribute to the development of the disease.

It is now necessary to understand how the characteristics of sleep, namely its duration, its disruption, possible sleep apnea or the regulation of sleep-wake cycles during adulthood, influence the risk of dementia at a later age. , note the researchers in their publication. This future work would make it possible to “identify windows of opportunity for therapeutic interventions aimed at reducing the risk or delaying the progression of dementia“, they continue.

Stay active, don’t smoke … and sleep well

Waiting, “encouraging good sleep hygiene may be especially important for people at high risk for dementia“, they recommend in their study. A piece of advice to add to the list of habits to adopt to keep a healthy brain: do not smoke, drink in moderation, stay active mentally and physically, eat a balanced diet and control its levels cholesterol and blood pressure.