Sleeping too little or too much can increase risk of getting dementia, study finds
Older adults who sleep six hours or fewer a night may have elevated risk for dementia and other cognitive issues, a new study finds.
Researchers at Stanford University measured seniors' (ages 65 to 85) dementia risk and cognitive abilities, finding higher risk in those patients who regularly slept six or fewer hours compared to those who slept seven or eight hours.
Those seniors who slept nine or more hours also had lower cognitive functions and other health issues, but the researchers didn't find the same high dementia risk in this group.
The findings demonstrate how important it is for adults to maintain a healthy sleep cycle, especially as they get older.
As adults age, it's common for their sleep patterns to change or become disrupted - leading to longer, shorter, or more irregular sleep.
This disruption may be linked to Alzheimer's and other forms of dementia, impacting seniors' ability to remember information, problem-solve, and go through everyday behaviors.
Sleep disruption can also be caused by - or heighten - depression, cardiovascular disease, and other conditions.
New research from Stanford University provides additional evidence for the connection between sleep and brain function. The study was published Monday in JAMA Neurology.
The Stanford study included health records from about 4,400 patients, all between the ages of 65 and 85. These patients had undergone brain scans and other cognitive tests, but hadn't been diagnosed with dementia.
This data was drawn from a long-term Alzheimer's investigation, conducted at 67 clinics in the US, Canada, Australia, and Japan.
The researchers grouped these patients according to how long they typically slept. Sleep times were self-reported by the patients, not measured by a sleep tracker.
A recommended sleep time for seniors is seven to eight hours, the researchers said. Six or fewer hours corresponded to short sleep, while nine or more hours corresponded to long sleep.
The Stanford researchers measured levels of beta amyloid, a protein in the brain that is typically found in high levels when a patient develops Alzheimer's.
In addition, the researchers used several tests for memory, attention, spatial skills, and executive function to identify patients' cognitive abilities.
Those patients sleeping for six hours or fewer a night were more likely to develop dementia, the researchers found. The low-sleep patients had higher levels of beta amyloid.
'Amyloid-β is one of the first detectable markers in the progression of Alzheimer's disease,' Joe Winer, postdoctoral researcher at Stanford and the study's lead author, told CNN.
The Stanford researchers found that patients with lower sleep also performed worse on memory tests, while those with higher sleep (nine or more hours) performed worse on executive function tests - which measure the brain's ability to switch between different tasks.
Both the low and high sleep patients were more likely to nap during the day, the researchers found. Low-sleep patients may have been compensating for a lack of sleep at night, while high-sleep patients may have simply been drowsy throughout the day.
In addition, both the low and high sleep patients had higher body mass index and symptoms of depression.
'The main takeaway is that it is important to maintain healthy sleep late in life,' Winer told CNN.