London, Oct 12 : Scientists have identified molecules in the blood that can detect dementia about two to five years before its onset, making the diagnosis of the condition -- via a simple blood test.

The biomarker discovered by researchers at the DZNE and the University Medical Center Gottingen (UMG) is based on measuring levels of microRNAs -- which influence the production of proteins and thus a key process in the metabolism of every living organism.

As the technique is not yet suitable for practical use, the scientists aim to develop a simple, low-cost blood test, similar to the rapid test for SARS-CoV-2, and can be applied in routine medical care to assess dementia risk.

According to the study data, presented in the scientific journal EMBO Molecular Medicine, microRNAs could potentially also be targets for dementia therapy.

"When symptoms of dementia manifest, the brain has already been massively damaged. Presently, diagnosis happens far too late to even have a chance for effective treatment. If dementia is detected early, the odds of positively influencing the course of the disease increase," said Andre Fischer, Professor at the Department of Psychiatry and Psychotherapy at UMG.

"We need tests that ideally respond before the onset of dementia and reliably estimate the risk of later disease. In other words, tests that give an early warning. We are confident that our current study results pave the way for such tests," Fischer added.

Through extensive studies in humans, mice and cell cultures, the researchers identified three microRNAs whose levels were associated with mental performance.

For this, they analysed data from both young, cognitively normal individuals and from elderly people with mild cognitive impairment.

The findings showed that in healthy individuals, levels of microRNAs correlated with mental fitness.

The lower the blood level, the better the subjects performed in cognition tests. In mice, in turn, this score increased even before the rodents started to show mental decline -- regardless of whether this was due to age or because they developed symptoms similar to those of Alzheimer's dementia.

Of those in whom the blood marker was highly elevated, about 90 per cent developed Alzheimer's disease within two years.

"We therefore see an increased blood level of these three microRNAs as a harbinger of dementia," Fischer said.

"We estimate that in humans this biomarker indicates a development that is about two to five years in the future."

A simple blood test may spot early signs of dementia