A new study has found that older adults who sleep 6 hours or less per night may be at a higher risk of developing dementia and other cognitive issues. Researchers at Stanford University assessed the risk of dementia among seniors aged 65 to 85 years and their cognitive abilities, revealing a greater risk in those who regularly sleep 6 hours or less compared to those who sleep 7 or 8 hours. Seniors who slept 9 hours or more also exhibited decreased cognitive function and other health problems, but researchers did not find the same risk of dementia in this group.
The findings highlight the importance of maintaining a healthy sleep cycle for older adults, especially as they age. It is common for adults to experience changes or disruptions in their sleep patterns, leading to longer, shorter, or more irregular sleep. This disruption may be linked to Alzheimer’s disease and other forms of dementia, affecting seniors' ability to recall information, solve problems, and carry out daily tasks. Sleep disruption can also result from depression, cardiovascular diseases, and other conditions.
The new study from Stanford provides additional evidence of the relationship between sleep and brain function, including health records from around 4,400 patients aged 65 to 85. These patients underwent brain scans and other cognitive tests but had not been diagnosed with dementia. Data were derived from a long-term Alzheimer's investigation conducted at 67 clinics in the United States, Canada, Australia, and Japan.
Researchers classified these patients based on their sleep duration. Sleep times were reported by the patients, without measurement by sleep trackers. Researchers recommended that older adults aim for 7 to 8 hours of sleep, with 6 hours or less classified as short sleep, while 9 hours or more corresponds to long sleep. Previous studies indicated that patients sleeping less than 6 hours and more than 9 hours experienced worse health outcomes, although short sleep tends to be more severe.
Stanford researchers measured levels of beta-amyloid, a protein in the brain often elevated when someone has Alzheimer's disease. Additionally, several tests on memory, attention, spatial skills, and executive function were used to assess patients' cognitive abilities. The study revealed that those who sleep for 6 hours or less per night were more likely to develop dementia, and these patients had higher beta-amyloid levels.
Jo Winner, a postdoctoral researcher at Stanford and the study's lead author, stated to CNN, "Beta-amyloid is one of the earliest markers that can be detected in the progression of Alzheimer's disease." He added, "In Alzheimer's, beta-amyloid proteins begin to accumulate throughout the brain and stick together in plaques."
The findings from Stanford align with previous research indicating that shorter sleep duration may be linked to dementia. The researchers found that patients experiencing sleep deprivation performed worse on memory tests, while those with longer sleep durations (9 hours or more) performed worse on executive function tests, which assess the brain's ability to switch between different tasks. Patients with longer sleep durations displayed normal levels of beta-amyloid, suggesting that their risk for dementia is not as severe as those suffering from sleep deprivation.
The study also found that both low and high sleep durations were associated with a greater likelihood of napping during the day. Additionally, patients with low and high sleep had higher body mass indexes and symptoms of depression. Winner emphasized to CNN, "The main takeaway is that it is important to maintain healthy sleep in advanced age."
