Researchers from the United States have shed light on why people experience more fragmented sleep as they grow older.
In a study of elderly individuals and people suffering from Alzheimer’s disease, the team showed that neural loss in a particular part of the hypothalamus seems to be linked to a decrease in sleep quality.
These findings may lead to new methods to diminish sleep problems in the elderly and prevent sleep-deprivation-related cognitive decline in people with dementia," says senior author Clifford Saper from the University of Toronto.
As people age, they generally find it more difficult to fall and stay asleep. This problem is particularly pronounced among Alzheimer’s sufferers, whose wakefulness and confusion can lead to night-time wandering.
As reported in the journal Brain, Saper and colleagues examined the brains of 45 individuals from the Rush Memory and Aging Project who had worn a wrist-watch actigraphy device for at least a week while they were alive. The device monitors all movements 24 hours a day and provides a good measure of the amount and quality of sleep a person gets. The patients were aged a mean of 89.2 years at the time of death and twelve had Alzheimer’s disease.
Immunohistochemistry and stereology techniques showed that the amount of neurons present in the intermediate nuclea of the hypothalamus was negatively associated with the amount of sleep fragmentation the subjects experienced.
Individuals with the highest proportion of galanin-immunoreactive intermediate nucleus neurons (more than 6,000) experienced less fragmented sleep than those with the lowest proportion (less than 3,000). Individuals who had Alzheimer’s disease were estimated to have around 2900 less of these neurons than those without the condition and among those who did have Alzheimer’s, the degree of sleep fragmentation also seemed to be linked to how many of these neurons were lost.
“A paucity of galanin-immunoreactive intermediate nucleus neurons is accompanied by sleep fragmentation in older adults with and without Alzheimer’s disease,” writes the team.
The loss of these neurons may be an important reason why older individuals often face sleep disruptions"