To investigate the link between sleep duration and the risk of developing Alzheimer’s disease, researchers at the University of Washington conducted a study on 100 older adults who undergo cognitive assessments each year.
The sleep quality of the volunteers was monitored for 4-6 nights using a portable encephalography device. Participants donated cerebrospinal fluid samples to measure levels of beta-amyloid – peptides that are a major component of amyloid plaques in Alzheimer’s disease – and tau protein, another marker of the disease. They also underwent a series of neuropsychological tests.
Volunteers who slept less than 4.5 hours or more than 6.5 hours a night showed the most significant cognitive decline over time. For those whose sleep duration was in this interval, the indicators remained stable. These results were confirmed even after adjusting the data for various factors, including age, gender, and amyloid-beta and tau protein levels.
“All this suggests that there is a time range, a” golden mean “of sleep duration,” – said the study authors.
The researchers noted that the quality and duration of sleep in older people may serve as another marker of an increased risk of Alzheimer’s disease in older people.
Earlier, researchers at the Harvard School of Medicine found that older people who took 30 minutes or more to fall asleep were 45% more likely to develop dementia within five years.
In addition, poor sleep quality, including the desire to take a constant nap during the day, and its duration of 5 hours or less, is closely associated with an increased risk of death from a range of other causes.