The link between sleep and Alzheimer’s diseaseis a complex one, and here at Medical News Today, we’ve been trying to illuminate it by reporting on the latest studies in the field.
One such study suggested that poor sleep may lead to brain proteins such as amyloid beta and tau becoming tangled, a known hallmark of the neurological condition.
Another study suggested that sleep disorders may be an early sign of Alzheimer’s disease, and although the study was observational, it found biological markers of the disease in the brains of people who reported insomnia or disrupted sleep.
Now, new research deepens our understanding of this complex relationship, as scientists find that disruptions in the sleep/wake cycle in completely asymptomatic people might signal the presence of preclinical evidence of Alzheimer’s disease.
Dr. Erik S. Musiek — an assistant professor of neurology at the Washington University School of Medicine in St. Louis, MO — is the first author of the study.
The scientists were prompted in their new study by previous animal and human studies that were conducted at Washington University, which revealed that levels of the Alzheimer’s-related brain protein amyloid beta go up and down at different times through the circadian rhythm. They also found that less sleep may lead to more amyloid beta in the brain.
They therefore set out to investigate circadian rhythms in seniors and checked their results by also carrying out a second study in mice. The findings are particularly significant given that Alzheimer’s-related brain damage can occur up to 20 years before any symptoms start to show, so early detection is crucial.
Causality remains unclear
The findings echo those of the mouse study published The Journal of Experimental Medicine. In it, mice were genetically engineered to have a dysfunctional circadian clock.
“Over 2 months, mice with disrupted circadian rhythms developed considerably more amyloid plaques than mice with normal rhythms,” explains Dr. Musiek.
“The mice also had changes in the normal, daily rhythms of amyloid protein in the brain. It’s the first data demonstrating that the disruption of circadian rhythms could be accelerating the deposition of plaques,” he adds.
Still, the researchers also emphasize the fact that the findings are too preliminary to tell whether or not Alzheimer’s causes body clock disruptions or vice versa. “At the very least, these disruptions in circadian rhythms may serve as a biomarker for preclinical disease,” Dr. Ju says.