Middle-aged adults who regularly sleep fewer than six hours a night are at greater risk of dementia, according to new research.
People aged between 50 and 70 with a pattern of consistently shorter sleeping periods face a 30 per cent higher risk of the condition, a study that tracked nearly 8,000 Britons over three decades found.
About 10 million new cases of dementia are reported worldwide every year and the study published on Tuesday in Nature Communications adds to evidence suggesting that disturbed sleeping patterns are a contributing factor.
Previous research has shown that mental illness and longer than average periods of sleeping are also linked to the disorder.
The latest paper examined the development of dementia over a longer period than most studies, which typically span fewer than 10 years, the authors said.
Researchers from Finland, France, the Netherlands and the UK studied data that tracked the health of 7,959 working people since 1985. The data came from a University College of London study, with participants self-reporting how long they slept, with their data backed up by that from wrist monitors.
It found that 521 of them had been diagnosed with dementia, with most of the cases emerging after the age of 70.
The study found that “normal” sleepers, getting seven hours a night, were most likely to be white, married men with sound mental health.
Depression and mood swings are also linked to changes in sleeping patterns. But the study failed to find a link between the small number of long sleepers in the study and dementia.
“The findings suggest sleep may be important for brain health in midlife,” the study found. “Future research may be able to establish whether improving sleep habits may help prevent dementia.”
A second study published on Tuesday showed a clear link between broken sleep and an increased risk of dying of heart disease.
The study of 8,001 men and women published in European Heart Journal found that women who most often emerged from deep sleep at night had nearly double the risk of dying from cardiovascular disease.