The team of researchers said that this could be a breakthrough in stopping the disease from progression by being targeted with new drugs. Professor Andre Fischer, the study’s lead author from University Medical Center G？ttingen said: “When symptoms of dementia manifest, the brain has already been massively damaged. “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.”

       The researchers used a method that measures small fragments of genetic material known as microRNAs.

       They discovered through analysing humans, mice and lab-grown cells that a specific molecular trio had a link to dementia.

       In trial, participants who had a higher than normal prevalence of these molecules, 90 percent went on to develop Alzheimer’s disease within the next two years.

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

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

       The researchers undertook a comparison of young, cognitively normal people and elderly people with mild cognitive impairment, which can lead to dementia.

       The results were revealing, and fitted “like pieces of a puzzle”.

       In the cognitively normal volunteers, the fewer the microRNAs they had in their blood, the better they performed in memory tests.

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       The experiments they performed on the mice and cells unveiled that the three microRNAs can lead to an inflammatory process in the brain.

       They also have an effect on neuroplasticity, which involved neurons connecting to one another.

       The scientists were able to block the three molecules by using drugs on mice, and this had promising results as it greatly improved their ability to learn.

       Professor Fischer said: “We intend to develop a simple test procedure for point-of-care screening.

       “Our goal is to have a low-cost test...used during routine check-ups in doctors’ practices.”

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       The findings were published in the journal EMBO Molecular Medicine and came from research teams at the German Center for Neurodegenerative Diseases and University Medical Center G？ttingen.

       Alzheimer's disease is most common in people over the age of 65 and risk of developing the disease and other types of dementia increases with age, affecting an estimated 1 in 14 people over the age of 65 and 1 in every 6 people over the age of 80.

       But around 1 in every 20 people with Alzheimer's disease are under the age of 65.

       Dementia affects around 920,000 people in the UK, and the number is expected to rise to two million by 2050 due to the ageing population.

       But breakthrough research could prove vital in fighting that prediction.