A study has revealed that a 1% decrease in deep sleep each year in individuals aged 60 and older can lead to a 27% rise in the risk of developing dementia
This study implies that preserving or improving deep sleep, also called slow-wave sleep, in older individuals may help prevent dementia. The study was led by Associate Professor Matthew Pase from the Monash School of Psychological Sciences and the Turner Institute for Brain and Mental Health in Melbourne, Australia.
Impact of deep sleep decline on dementia risk
This research involved 349 participants, all of whom were over 60 years old and were part of the Framingham Heart Study. The participants undertook two overnight sleep studies during two-time frames, specifically between 1995 to 1998 and 2001 to 2003, with an average of five years between the two studies.
These participants were carefully monitored for the development of dementia from the time of the second sleep study up until 2018. The researchers observed that, on average, there was a decline in the amount of deep sleep between the two study periods, indicating a loss of slow wave as time went on.
During the 17-year follow-up period, 52 cases of dementia emerged. Even after accounting for variables such as age, gender, genetic factors, smoking habits, use of sleep medications, antidepressants, and anxiety medication, it was revealed that for each annual percentage decrease in deep sleep, there was a corresponding 27 per cent increase in the risk of dementia.
Genetic risk factors and slow-wave sleep
“Slow-wave sleep, or deep sleep, supports the ageing brain in many ways, and we know that sleep augments the clearance of metabolic waste from the brain, including facilitating the clearance of proteins that aggregate in Alzheimer’s disease,” Associate Professor Pase said.
“However, to date, we have been unsure of the role of slow-wave sleep in the development of dementia. Our findings suggest slow-wave sleep loss may be a modifiable dementia risk factor.”
“Our findings suggest slow-wave sleep loss may be a modifiable dementia risk factor.”
Key finding
Associate Professor Pase emphasised that the Framingham Heart Study is a distinct community-based group with recurrent overnight polysomnographic (PSG) sleep studies and continuous monitoring to detect new dementia cases.
He explained that they conducted these sleep studies to investigate the alterations in slow-wave sleep as individuals aged and to determine whether shifts in the percentage of slow-wave sleep were connected to the likelihood of developing dementia in later life, spanning up to 17 years.
They further explored whether there was a connection between genetic susceptibility to Alzheimer’s Disease and indications of early neurodegeneration in brain volume with a decrease in slow-wave sleep.
Their findings indicated that a genetic predisposition to Alzheimer’s disease, as opposed to brain volume, was linked to more rapid reductions in slow-wave sleep.
