The importance of quality and sleep duration The French are often unaware of this and sometimes neglect their nights and naps. What is the link between sleep duration and cognitive decline observed in the elderly? The monitoring of a large population cohort has recently provided some answers to this question. Explanations.
Sleep duration and cognitive decline
Sleep, like diet, is one of the essential pillars of health. Lack of sleep can have a profound impact on mental health, negatively affecting :
- Mood ;
- Behaviour;
- The brain ;
- The body as a whole.
Getting good quality sleep of the right length is therefore essential to maintain physical and mental health, but probably also to limit the risk of cognitive decline related to age. This was the focus of a recent study of a cohort of 28,756 people aged over 50 living in the UK and over 45 living in China. The researchers assessed each participant's :
- Their cognitive functions ;
- Their sleep duration.
A link revealed between sleep duration and cognitive decline
A total of 9,254 English and 10,811 Chinese participants completed the study. Assessment of cognitive ability, using several commonly used tests, revealed that participants sleeping less than four hours per night or more than ten hours per night declined more rapidly than participants in the control group, who slept about seven hours per night.
This link between the sleep duration and the cognitive decline Thus, the relationship was U-shaped, suggesting that both excess sleep and sleep deprivation would be negative for cognitive function. This link remained significant after adjusting the data for other parameters, such as :
- Sex;
- Age ;
- Body Mass Index (BMI);
- Blood pressure ;
- Education level ;
- Smoking or drinking alcohol.
Too much sleep is as bad as too little
More specifically, the cognitive function most affected by sleep duration was memory, which is the very function directly affected in the Alzheimer's disease and other dementias. Although previous studies had already pointed the finger at sleep deprivation in the impairment of memory capacity in children, adolescents and adults, no link had yet been demonstrated between excessive sleep and cognitive decline.
Even if the mechanisms associating sleep duration and the impact on cognitive functions remain to be clarified, this study underlines the importance of getting enough sleep, but not too much, in order to preserve one's cognitive capacities, particularly for people over 45 years of age. At the same time, for patients suffering from a lack (insomnia) or chronic excess (hypersomnia) of sleep, a regular assessment of cognitive functions would be interesting to integrate into their management.
Estelle B., Doctor of Pharmacy
English (UK) 
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