Short sleep duration in midlife is associated with the increased risk of dementia in later life, independent of sociodemographic, behavioral, cardiometabolic and mental health factors, according to a new study published in the journal Communicating Nature.
“Changes in sleep patterns are common in people with Alzheimer’s disease and other dementias,” says Dr. Séverine Sabia, a researcher at the Université de Paris and the Department of Epidemiology and Public Health at University College London, and colleagues.
“These changes are thought to result from the deregulation of the sleep-wake cycle due to pathophysiological processes in dementia, particularly those affecting the hypothalamus and brain system.”
“Apart from sleep disturbance, there is growing interest in the link between sleep duration and dementia.”
“Observational studies show that short and long sleep duration is associated with an increased risk of cognitive decline and dementia.”
“Some studies also indicate that a change in sleep duration in older adults is linked to the risk of dementia.”
The researchers used data from 7,959 British adults who are part of the Whitehall II cohort study.
Participants self-reported sleep duration six times between 1985 and 1988 (age range: 35 to 55 years) and 2015 and 2016 (between 63 and 86 years) allowing the authors to measure sleep duration at 50, 60 and 70 years of age.
Some participants also wore viewing accelerometers over a full week, to obtain an objective measure of sleep duration.
A total of 521 participants had developed dementia by the end of the 2019 study period.
The scientists found that those who slept six hours or less each night in middle age were significantly more likely to develop dementia later in life, compared to those who slept seven hours a night .
They found no significant association between sleeping for eight hours or more, and risk of dementia.
They found that society was independent of potentially confusing factors such as mental health, or differences in behavior, sociodemographic status, or heart health.
“Sleep problems are known to occur in people with dementia, but it remains unclear whether the duration of mid-life sleep affects the risk of developing dementia in later life,” said Dr. Sabia.
“By using a very long follow-up period, we have found that short-term sleep in mid-life, assessed more than 25 years before the mean age at onset of dementia, is associated with end-of-life dementia risk.”
“While we cannot confirm that not having enough sleep actually increases the risk of dementia, there are plenty of reasons why a good night’s sleep could be good for brain health. These findings confirm the importance of sleep hygiene to health. ”
“We know that sleep is important to our brain health, as it is about learning and memory, clearing brain waste, and our brain’s ability to stay healthy,” said Dr. Archana Singh-Manoux, also from the Université de Paris and University College London.
“We need a better understanding of how the characteristics of sleep might shape our risk of dementia, as this could help researchers develop new ways to reduce the risk of dementia, or delay its development.”
S. Sabia et al. 2021. Association of sleep duration in middle age and old age with dementia cases. Nat Commun 12, 2289; doi: 10.1038 / s41467-021-22354-2