A Simple Blood Test May Predict Dementia Years Before Symptoms Appear

The research findings primarily focus on individuals with a sleep disorder but may have broader implications.

A recent study suggests that a simple blood test could help predict the onset of dementia years before symptoms appear in individuals with a specific sleep disorder.

Idiopathic REM sleep behavior disorder (iRBD) causes people to physically act out their dreams while sleeping. This condition is strongly linked to a high risk of developing Parkinson’s disease and Dementia with Lewy Bodies—a form of dementia characterized by memory loss, cognitive decline, vivid visual hallucinations, and movement difficulties similar to Parkinson’s.

Researchers at McGill University have found that a blood test initially designed to detect Alzheimer’s disease may also help identify iRBD patients who are most likely to develop dementia with Lewy bodies. The test works by analyzing two proteins in the blood that serve as biomarkers for Alzheimer’s, potentially offering an early warning for those at risk.

“Detecting dementia risk early could have significant implications for how doctors guide patients, helping them plan for the future and potentially allowing for more personalized, effective treatments,” said Dr. Ronald Postuma, a Professor in McGill’s Department of Neurology and a clinical researcher at The Neuro (Montreal Neurological Institute-Hospital).

Researchers followed 150 iRBD patients, testing their blood for the biomarkers and tracking their health annually. Remarkably, the blood test, taken four years before, predicted dementia in almost 90 percent of the patients who later developed the disease.

Finding links between brain diseases

This study, published in the journal Brain, also suggests the early stages of Parkinson’s and Alzheimer’s have more in common than previously thought.

“Our findings suggest that Alzheimer’s treatments could also be tested in patients with this sleep disorder. Perhaps, if treatments start early enough, Dementia with Lewy Bodies can be prevented,” said first author Dr. Aline Delva, who was a research fellow at The Neuro during the study.

The research team plans to expand the study to confirm how well the test can predict dementia risk in patients with diagnosed Parkinson’s disease as well as other populations at risk for Dementia with Lewy Bodies.

Reference: “Plasma pTau181 and amyloid markers predict conversion to dementia in idiopathic REM sleep behaviour disorder” by Aline Delva, Amélie Pelletier, Emma Somerville, Jacques Montplaisir, Jean-François Gagnon, Gwendlyn Kollmorgen, Tony Kam-Thong, Thomas Kustermann, Venissa Machado, Ziv Gan-Or and Ronald B Postuma, 6 January 2025, Brain.

The study was supported by the Canadian Institutes of Health Research and F. Hoffmann-La Roche Ltd.