Once again about the dangers of lack of sleep
Lack of sleep in adulthood has been linked to dementia in old age
Anastasia Kuznetsova, N+1
Sleep duration of less than seven hours in 50-60 years is associated with an increased risk of dementia, regardless of sociodemographic data, lifestyle, risk of cardiovascular and neurological diseases. The lowest prevalence of dementia per 1,000 people was observed in the seven-hour sleep group. Such results were obtained by neurophysiologists after analyzing the data of 7959 participants of the Whitehall II cohort from 1985 to 2015. The study is published in Nature Communications (Sabia et al., Association of sleep duration in middle and old age with incident of dementia).
Dementia is a syndrome in which memory deteriorates, behavior changes and the ability to perform daily actions is lost. This disease is characteristic of the elderly, but it is not a normal sign of aging. Around 50 million people live with dementia worldwide, and almost 10 million new cases of the disease are detected annually.
Sleep disorders are common in people with dementia. They arise due to a failure of circadian rhythms due to pathological processes in the hypothalamus and in the brain stem. There have also been works on the relationship of sleep duration with the risk of dementia, but most of them took a period of less than ten years, and the development of dementia is a long process, often developing for 20 years or more. Also, studies were rarely conducted in people under 65 years of age, which did not allow us to assess the impact of sleep in earlier periods of life.
A group of scientists from England, the Netherlands, Finland and France led by Professor Archana Singh-Manoux from The University of Paris decided to test the relationship between sleep duration and the risk of dementia by including middle-aged people in the study. The data of 7959 people who participated in the study were used in the work Whitehall II, which began in 1985-1988. A new data collection was carried out every 4-5 years (the last one was in 2015-2016). Sleep duration was assessed using a questionnaire. For each participant, information was taken on three time cut-offs: 50, 60 and 70 years. Data on sleep duration was divided into three categories: short (≤6 hours), normal (7 hours) and long (≥8 hours). In 2012-2013, the researchers also performed actiography (a non-invasive method for monitoring rest/activity cycles) in 3,888 participants. Data on the development of dementia were obtained from three national registers (the national hospital episode statistics (HES) database, the Mental Health Services Data Set, the mortality register). Using multivariate analysis, scientists corrected for the influence of gender, race, education, civil status, smoking, alcohol consumption, physical activity and diet, as well as the risk of cardiovascular and neurological diseases. A regression model of Cox's proportional risk with age was used as a time scale for calculating the association with dementia.
The average age of onset of dementia in the study was 77.1 years. The lowest prevalence of dementia per 1,000 people was observed in the seven-hour sleep group. When adjusted for socio-demographic factors, short sleep duration was associated with an increased risk of dementia regardless of age (p< 0.02), when data on lifestyle, risk of cardiovascular and neurological diseases were included in the correction, the relationship remained significant for the age of 50 years (HR=1.22, 95% CI=1.01-1.48) and 60 years (HR = 1.37, 95% CI=1.10-1.72). Actiography data confirmed the results obtained: compared with a seven-hour sleep, sleep lasting six hours or less was associated with a higher risk of dementia (HR=1.7, 95% CI=1.03-2.79), and no such association was observed for sleep lasting eight hours or more.
Scientists have concluded that sleeping less than seven hours a day in middle age increases the risk of developing dementia in old age. The explanation most likely lies in the special role of sleep in learning, memory, synaptic plasticity and "cleansing" of the brain. Sleep hygiene is especially important for patients at high risk of developing dementia.
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