Sleeping less than 6 hours a night linked to increased dementia risk

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Peer-reviewed: This work was reviewed and scrutinised by relevant independent experts.

Observational study: A study in which the subject is observed to see if there is a relationship between two or more things (eg: the consumption of diet drinks and obesity). Observational studies cannot prove that one thing causes another, only that they are linked.

Survey: A study based solely on people’s responses to a series of questions.

People: This is a study based on research using people.

Those who sleep six or fewer hours a night could be at higher risk of dementia later in life, according to UK researchers. Using survey data from 7959 people involved in a health study since 1985, researchers looked at sleep data from when the participants were 50, 60 and 70 years old against those who went on to be diagnosed with dementia. At all ages, less sleep was associated with a higher risk of dementia, with a 30 per cent increased risk for those who consistently slept less throughout the years. Studies of this kind can not prove that lack of sleep causes dementia, only that there is a link between sleep duration and dementia risk.

Journal/conference: Nature Communications

Link to research (DOI): 10.1038/s41467-021-22354-2

Organisation/s: Université de Paris, France

Funder: The Whitehall II study is supported by grants from the National Institute on Aging, NIH (R01AG056477, RF1AG062553); the Wellcome Trust (221854/Z/20/Z); the UK Medical Research Council (R024227, S011676); and the British Heart Foundation (RG/16/11/ 32334). In addition, M.K. was supported by grants from NordForsk (70521, the Nordic Research Programme on Health and Welfare), the Academy of Finland (311492, 329202), and Helsinki Institute of Life Science (H970). A.S. is funded by the UCL/ Wellcome Trust Institutional Strategic Support Fund (204841/Z/16/Z) and by the University College London Hospitals’ (UCLH) National Institute for Health Research (NIHR) Biomedical Research Centre (BRC). S.S. is supported by the French National Research Agency (ANR-19-CE36-0004-01).

Media release

From: Springer Nature

Health: Sleep duration in middle age associated with dementia risk

Regularly sleeping six hours or fewer per night during middle age is associated with a greater risk of dementia, according to a new study of nearly 8,000 British adults followed over 25 years, published this week in Nature Communications. These findings cannot establish cause and effect, but suggest a link exists between sleep duration and dementia risk.

Nearly 10,000,000 new cases of dementia are reported worldwide every year. A common symptom is altered sleep; however, there is growing evidence to suggest sleep patterns before dementia onset may contribute to the disease. Time spent sleeping is linked to dementia risk in older adults (65 years and older), but it is unclear whether this association is also true for younger age groups.

Séverine Sabia and colleagues analysed survey data from UCL’s Whitehall II study that has examined the health of 7,959 British individuals since 1985. Participants self-reported their sleep duration, and some wore watch accelerometers overnight to confirm this was an accurate estimate. The study shows higher risk of dementia in those sleeping six or fewer hours per night at the age of 50 or 60. There was also a 30% increased dementia risk in those with consistently short sleeping patterns from middle to older age (from 50 to 70 years), irrespective of cardiometabolic or mental health issues (known risk factors for dementia).

The findings suggest sleep may be important for brain health in midlife. Future research may be able to establish whether improving sleep habits may help prevent dementia.

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