Sleep Deprivation Tied to Early Onset of Alzheimer's Disease

Sleep deprivation (SD) and sleep disturbances are tied to an early onset of Alzheimer’s disease (AD), according to a study published in the February issue of the Neurobiology of Aging.

To understand SD’s role in the onset of AD, Domenico Praticò, MD, and colleagues at Temple University evaluated the biological and functional effects in mice that were subjected to sleep disturbances for an 8 week period and compared them to mice under normal sleeping conditions.

One group of mice was subjected of a normal schedule of 12 hours light and 12 hours of darkness. The second group was put under conditions consisting of 20 hours of light and 4 hours of darkness, which resulted in a lack of sleep. To replicate the state of a 50-60 year old human patients’ brain, researchers used mice aged 14-15 months for their study.

Researchers discovered negative effects in the SD mice’s memory and learning abilities. Although researchers initially didn’t see any differences in the two groups’ soluble amyloid- β peptide levels, Praticò, who led the study, said upon further investigation, there were differences in other brain levels.

When the researchers tested the mice for memory, the group with reduced sleep showed difficulty in their working, retention memory, and learning ability.

“Surprisingly, we didn’t see any difference between the 2 groups in the amyloid plaques,” Praticὸ said. “However, we did observe that the sleep disturbance group had a significant increase in the amount of tau protein that became phosphorylated and formed the tangles inside the brain’s neuronal cells.”

Tau protein is mainly responsible for cellular health. However, phosphorylated tau can disrupt the synaptic connection between cells, causing nutrients or chemicals not to be transported from one cell signal to another.

Researchers believed their findings provided further clarity about the effect sleep, or lack thereof, has on AD.

“The big biological question that we tried to address in this study is whether sleep disturbance is a risk factor to develop Alzheimer’s or is it something that manifests with the disease,” Praticò said.

Additionally, investigators said there are available solutions for this problem, as SD can be rectified through therapeutic strategy, which could lead to prevention or slowing of AD to at-risk individuals.

“We can conclude from this study that chronic sleep disturbance is an environmental risk factor for Alzheimer’s disease,” Praticò said. “But the good news is that sleep disturbances can be easily treated, which would hopefully reduce the Alzheimer’s risk.”