Study finds higher rate of dementia in those who get less sleep

People in their 50s and 60s who do not get more than six hours sleep a night appear to have a higher risk of developing dementia in later life, a major new study from University College London (UCL) suggests.

Those who persistently fail to get at least that much sleep were almost a third more likely to develop dementia, compared to those with normal sleep duration, the research found.

The study was led by the UCL and Inserm researchers, using data from 7,959 British adults, with the findings published in Nature Communications.

The adults self-reported their sleep duration six times between 1985 (when the age range of participates was 35 to 55 years) and 2015, enabling the researchers to gauge sleep duration at ages 50, 60, and 70.

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Some participants also wore monitors over a full week, to derive an objective measure of sleep duration. By the end of the study period in 2019, 521 of the participants had developed dementia.

The researchers found that those 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.

They did not find any significant link between sleeping for eight or more hours, and dementia risk. The researchers also found that the association, where it did exist, was independent of factors such as mental health, sociodemographic status or heart health.

“Previous studies reported an increased in dementia risk among those who sleep for longer than average, but results were inconsistent,” they said.

“Further studies, including more individuals with long sleep, will be needed to understand the role of sleep duration in dementia risk.”

Dr Séverine Sabia, lead author and research associate at the Department of Epidemiology & Public Health at UCL, said sleep problems are known to occur in people with dementia, but it has been unclear whether sleep duration in midlife affects the risk of developing dementia at older ages.

“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,” she said.

“While we cannot confirm that not sleeping enough actually increases the risk of dementia, there are plenty of reasons why a good night’s sleep might be good for brain health.”