A good night’s sleep clearly has an impact on dementia risk: People who regularly sleep less than six hours by age 50 have a 30 percent higher risk of developing dementia later. This is shown by the evaluation of a long-term study from Great Britain.

The cohort study evaluated data from nearly 8,000 participants, more than 521 of whom had suffered from dementia over the course of 25 years, with an average of 77 years. Those with a normal night’s sleep (defined as an average of seven hours) had the lowest risk of dementia. The risk was 30 percent higher for participants who regularly slept less than six hours — regardless of how healthy the participants lived and whether they had previous illnesses. The researchers found no association between the risk of dementia and prolonged sleep of more than nine hours, although the number of excessively late sleepers in the study was also very small.

An important result of the study is that reduced nighttime sleepiness and the risk of dementia were independent of mental illnesses such as depression, which may also be associated with sleep disorders. However, the researchers point out that the present work is an observational study that does not allow any clear conclusions to be drawn about cause and effect. Still, the message may be that good sleep hygiene is fundamentally beneficial to health – particularly to the central nervous system.

Sleep disorders are characteristic of many diseases, especially neurodegenerative diseases such as dementia. This is probably due to disturbances in sleep-wake rhythms due to dementia-related changes in the hypothalamus and brain stem. So far, it has not been clear whether there is a link between a person’s sleep duration at night and the risk of dementia. Results from previous studies were conflicting, and many only had follow-up periods of less than ten years and could not definitively answer the question as to why dementia develops over a long period of time.

What did I do 10.1038/s41467-021-22354-2