People who continuously sleep for six hours or less a night are roughly 30 per cent more likely to develop dementia, according to the findings published in online journal Nature Communications.

“Sleep problems are known to occur in people with dementia, but it remains unclear whether sleep duration in midlife affects the risk of developing dementia at older ages,” said lead author Dr Séverine Sabia, UCL Epidemiology & Public Health and INSERM.

“Here, by using a very long follow-up period, we have found that short duration sleep in midlife, assessed more than 25 years before mean age at dementia onset, is associated with dementia risk in late life.”

Data was collected from 7,959 British adults who are part of the Whitehall II cohort study, based at University College London (UCL). The participants self-reported their sleep duration six times between 1985-1988, aged between 35-55 years, and 2015-2016, aged between 63-86 years, to enable the researchers to gauge sleep duration at ages 50, 60, and 70. As a result, 521 of the participants had developed dementia by the end of the study period in 2019.

The data revealed that the people who slept six hours or less each night while middle-aged were significantly more likely to develop dementia later in life, compared to those who slept seven hours per night. There was no significant link found between sleeping for eight or more hours, and dementia risk. The association was independent of factors such as heart health, mental health or differences in behaviour, such as sociodemographic status, according to the researchers.

“We know that sleep is important to our brain health, as it is involved in learning and memory, waste clearance from the brain, and the ability of our brain cells to remain healthy,” said senior author Dr Archana Singh-Manoux, UCL Epidemiology & Public Health and INSERM. “A better understand of how sleep features might shape our risk of dementia is needed, as this might help researchers develop new ways to reduce the risk of dementia, or to delay its progression.”