Lack of Sleep Linked to Increased Risk of Dementia

Lack of sleep increases risk of dementia
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A long-term study has found that sleeping less than six hours a night in midlife can increase a person’s risk of dementia by 30%.

While as a child you may have hated going to sleep, as an adult you likely cherish every moment of it. This state of slumber not only helps recharge your body, but also your brain; allowing it to clear out toxins. According to the Mayo Clinic, the recommended amount of sleep for adults is 7 to 9 hours. Certain medications, aging, presence of diseases, neurological problems, and mental health problems can alter the sleep duration. A lack of sleep can affect your immune system, brain function, and your overall health. Although changes in sleeping patterns are a common feature of dementia, it is unclear whether the duration of sleep affects the incidence of the disease. However, a UK study has now found evidence of a lack of sleep increasing the risk of dementia later in life.

The long-term study followed nearly 8,000 participants, aged 50 years, for a duration of 25 years. Over the duration of the study, the participants underwent assessment for their sleep duration at age 50, 60, and 70. Those with a sleep duration of 7 hours per night were labelled as normal. Moreover, less than 6 hours of sleep was labelled as short, and more than 8 hours was labelled long.

The researchers then linked the data to their dementia diagnosis as per their electronic health records. More than 500 of the participants went on to develop dementia over the span of the study. They also collected information on the patients’ history of smoking, health conditions, mental health disorders, weight, and physical activity.

Irrespective of Other Factors

Results showed that those who slept for less than 6 hours at age 50 and 60 had a higher risk of dementia; compared to those with a normal sleep duration (7 hours). 50-year-olds with a sleep duration of 6 hours had a 22% higher risk of developing dementia. Whereas those aged 60 years had a 37% higher risk of developing the disease. Moreover, persistent short sleep duration causes a 30% increased dementia risk among the participants. The risk remained high despite adusting for ‘sociodemographic, behavioural, cardiometabolic, and mental health factors.’

This is the largest study to establish a link between sleep and the risk of dementia. However, researchers argue that it does not establish a cause and effect. Furthermore, it is unclear as to whether the lack of sleep is a consequence of dementia or a cause for the disease.

Even though we can’t say sleep duration has a causal impact on dementia, it would be good to encourage good sleep hygiene

Séverine Sabia, lead author

Nevertheless, the study provides strong evidence for establishing poor sleep as a risk factor for dementia. The authors of the study recommend that older adults avoid the use of electronic devices at least 30 minutes before bedtime to improve their quality of sleep.


Sabia, S., Fayosse, A., Dumurgier, J. et al. Association of sleep duration in middle and old age with incidence of dementia. Nat Commun 12, 2289 (2021).


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