Link Between Alzheimer’s Disease and Poor Sleep Suggested in New Study

Ana de Barros, PhD avatar

by Ana de Barros, PhD |

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Alzheimer's and sleep habits

Lack of sleep on a regular basis or waking up several times during the night may be harmful to the brain and increase the risk of developing Alzheimer’s disease, according to recent evidence.

Patients with Alzheimer’s disease tend to sleep poorly and stay awake more often at night. However, researchers have been unsure if poor sleep plays a role in the development of Alzheimer’s, or if it is an early symptom of the disease. Now, evidence from new studies further highlights the association between poor sleep and dementia.

In the study, “Self-Reported Sleep and Beta-Amyloid Deposition in Community-Dwelling Older Adults,” published in JAMA Neurology, Johns Hopkins Bloomberg School of Public Health researchers discovered that people with poor sleep patterns are more likely to exhibit an increase in brain levels of beta-amyloid, a toxic protein that forms plaques in the brains of patients with Alzheimer’s disease.

Researchers examined 70 older adults with a mean age of 76. Participants were part of the ongoing Baltimore Longitudinal Study of Aging. The researchers used brain scans and found that those who said they got the least sleep — fewer than five hours a night — or who slept fitfully had higher levels of beta-amyloid in the brain compared with those who slept more than seven hours a night.

Researchers couldn’t determine if poor sleep led to acceleration in the accumulation of beta-amyloid, or if beta-amyloid accumulation was caused by poor sleep. Both may the true. The researchers suggested that studies should examine the relationship between poor sleep and beta-amyloid accumulation, and that studies are needed “to determine whether optimizing sleep can prevent or slow Alzheimer’s disease progression.”

“These findings are important, in part because sleep disturbances can be treated in older people,” Dr. Adam Spira, the study’s lead author, said in a news release. “To the degree that poor sleep promotes the development of Alzheimer’s disease, treatments for poor sleep or efforts to maintain healthy sleep patterns may help prevent or slow the progression of Alzheimer’s disease.”

Another study titled “Sleep Initiated Fluid Flux Drives Metabolite Clearance from the Adult Brain,” published in the journal Science, suggests that one reason why poor sleep may be associated with the development of Alzheimer’s disease is that sleep may be a biological mechanism whose primary function is to remove toxic molecules from the brain. Using mice models, University of Rochester Medical School researchers discovered that when mice slept, their brain cells shrank, leaving more space for fluids to flow through the brain. This increased flow flushed harmful waste products like beta-amyloid.

“Sleep changes the cellular structure of the brain. It appears to be a completely different state,” said study author Dr. Maiken Nedergaard. Similar results have been observed in other animal studies, and if these findings are proved to occur in humans, they could explain how sleep may help to protect the brain.

In a third study, “Modification of the Relationship of the Apolipoprotein E E4 Allele to the Risk of Alzheimer’s Disease and Neurofibrillary Tangle Density by Sleep,” published in JAMA Neurologyresearchers from the University of Toronto discovered that sound sleep appeared to dull the consequences of APOE-E4, a gene known to increase the risk of developing Alzheimer’s disease.

Researchers examined about 700 elderly men and women, monitoring their sleep and cognitive status. At the start of the study, none of the participants had dementia. After six years of follow-up, 98 of the study participants had developed Alzheimer’s and 201 had died. The brains of the participants were examined for evidence of brain plaque and tangles found in patients with Alzheimer’s disease.

The team discovered that people carrying the APOE-E4 gene and those who had quality sleep were better able to preserve memory and thinking skills. Among the participants who died, those who had poor sleep were more likely to present the brain plaques and tangles.

Evidence from previous studies indicates that poor sleep can cause thinking and memory problems even in people who are healthy. People suffering from sleep apnea, a disorder that causes sleepers to awaken several times during the night, has also been associated with memory problems and to an increased risk for developing dementia.

It is common for older people to struggle with poor sleep and sleep apnea, so people should not be alarmed that they are at risk for Alzheimer’s. However, a good night’s sleep is critical for a healthy lifestyle – and might help to prevent Alzheimer’s.