Tiny Fragments of RNA in the Blood Signal Dementia Risk

Scientists have discovered a novel biomarker in the blood that acts as an early warning sign for dementia: microRNA. These small, single-stranded RNA molecules are a distinct class of biological regulators that orchestrate the way genes are expressed, influencing many complex processes throughout the body.

In a study featured in EMBO Molecular Medicine, researchers led by André Fischer from the German Center for Neurodegenerative Diseases were motivated by finding biological red flags that can signal the potential for dementia onset long before the symptoms begin. 

“Presently, diagnosis happens far too late to even have a chance for effective treatment,” said Fischer. “If dementia is detected early, the odds of positively influencing the course of the disease increase.”

The team used a variety of experimental approaches in their study: animal models, cell cultures, and the analyses of clinical data from both healthy individuals and those with mild cognitive impairment. 

A deep dive revealed a clear pattern—levels of three microRNAs were closely linked to mental fitness levels. Fischer and colleagues also found that patients who had high levels of this biomarker in their blood samples had a 90 percent chance of going on to receive an Alzheimer’s diagnosis within two years. The team estimates that the presence of these microRNAs in circulation is indicative of dementia development within a two- to five-year timeframe.

Interestingly, the three microRNAs are not just clinical biomarkers but also have the potential to be drug targets to slow the neurodegenerative process. Experiments in mouse models of dementia revealed that drugs that specifically blocked these microRNA improved the animals’ learning abilities. “We’ve observed this in mice with age-related mental deficits, as well as in mice with brain damage similar to that occurring in Alzheimer’s disease,” said Fischer.

Ongoing work by the team is focused on translating their findings into a practical, low-cost, easy-to-use test for the microRNA signatures that doctors could deploy during routine medical checkups to catch dementia in their patients earlier.