UCL data of 10,000 volunteers shows cases 30% higher among those who slept poorly in their 50s, 60s and 70s
People who regularly sleep for six hours or less each night in middle age are more likely to develop dementia than those who routinely manage seven hours, according to a major study into the disease.
Researchers found a 30% greater risk of dementia in those who during their 50s, 60s and 70s consistently had a short night’s sleep, regardless of other risk factors such as heart and metabolic conditions and poor mental health.
The study does not prove that sleeping too little causes dementia, since sleep loss itself may be one of the earliest symptoms of the disease. But some scientists believe the results bolster evidence that persistent poor sleep may at least contribute to the neurodegenerative disease.
Researchers do not know whether improving sleep can reduce the risk of dementia, but sleep is known to clear toxic waste from the brain. One hypothesis is that when people sleep less, this process becomes impaired.
“These findings suggest that sleep duration might be a risk factor for dementia in later life,” said Dr Séverine Sabia, an author of the study at the University of Paris. “I cannot tell you that sleep duration is a cause of dementia but it may contribute to its development.”