A restful night’s sleep is crucial for maintaining body health and functionality.
Scientists have identified the sleep phase that lowers dementia risk, according to Science Alert and JAMA Neurology.
A restful night’s sleep is crucial for maintaining body health and functionality. Its significance extends beyond common assumptions, scientists assert.
Research indicates that with age, dementia risk rises without sufficient deep (slow-wave) sleep. A study shows that in individuals over 60, dementia likelihood increases by 27% when 1% of deep sleep is lost annually.
Deep sleep, part of the 90-minute sleep cycle, lasts 20-40 minutes. This restorative phase slows brain waves and heart rate, lowers blood pressure, strengthens muscles, bones, and the immune system, and prepares the brain for new information.
Neuroscientist Matthew Pace of Monash University explains that slow-wave or deep sleep supports the aging brain by facilitating the removal of metabolic waste, including proteins linked to Alzheimer’s disease.
Previously, the exact role of deep sleep in dementia development was unclear. Findings suggest losing this phase may be a modifiable and controllable risk factor, Pace adds.
Pace and colleagues from Australia, Canada, and the US studied 346 Framingham Heart Study participants. They underwent two sleep studies, from 1995-1998 and 2001-2003, with a five-year gap.
Participants, over 60 in 2020 and without dementia during the 2001-2003 studies, provided data on the relationship between deep sleep and dementia. Researchers compared polysomnography sleep study data and tracked dementia development through 2018.
“We examined deep sleep changes with age and whether slow-wave sleep percentage changes relate to dementia risk up to 17 years later,” Pace states.
During the follow-up, 52 dementia cases were recorded. Deep sleep duration declined after age 60, peaking in loss between ages 75-80, then stabilizing.
Comparison of sleep studies showed a 27% increased dementia risk with each annual deep sleep percent decline. Focusing on Alzheimer’s, this risk rose to 32%.
The Framingham Heart Study tracks health indicators, including hippocampus shrinkage—a precursor to Alzheimer’s—and cardiovascular disease factors. Low deep sleep levels correlate with increased cardiovascular risk, medications affecting sleep, and the APOE ε4 gene, linked to Alzheimer’s.
“We discovered genetic Alzheimer’s risk factors relate to accelerated deep sleep decline, not brain volume,” Pace explains.
While clear, these links don’t prove lack of deep sleep causes dementia. Dementia-related brain processes may also cause sleep loss. Further research is necessary for full understanding, researchers state.
Meanwhile, prioritizing quality sleep remains vital for more than memory enhancement. Specific steps can increase deep sleep hours, scientists suggest.
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