New York: A 30-minute test that can detect unusual brainwave patterns may be able to detect Alzheimer’s ten years before symptoms emerge.

Researchers at New York University Medical School say the state of the art, electroencephalograph (EEG) can detect subtle changes that could signify the first signs of Alzheimer’s. It records brainwave patterns which appear to show early signs of mental deterioration before they result in memory loss and other devastating symptoms.

The machine has been used for some years to diagnose seizures and brain tumours and the researchers say it is around 95 per cent accurate in identifying those who would decline in mental function and those who would not. It was tested in a study of 44 people between the ages of 64 and 79 who felt their memories were faltering.

They were given a battery of neuropsychiatric and other tests which revealed their brain function was normal for their age.

But each volunteer was given an initial EEG test, followed by several more over the next seven to ten years.

Over this period, 27 of the 44 volunteers developed mild cognitive impairment or full-blown dementia, and 17 remained stable.

By checking the pattern of the scans, the researchers found certain signs on the initial EEG linked with future deterioration.

In particular, a brain wave called theta was excessive in people who would eventually decline, and a slowing of the electrical signals coming from the brain.

Study leader Dr Leslie Prichep warned that the test would have to be checked against much larger groups of people before it could become a standard screening test for Alzheimer’s.

Alzheimer’s is the most common cause of dementia and more new cases are diagnosed as more people live longer.

For some sufferers new drugs can delay the progress of devastating symptoms such as memory loss and erosion of the ability to do everyday things such as washing, but there is currently no cure.

A Swedish study found that those in their late 40s and early 50s could cut the risk of developing dementia by roughly half if they kept active.

And those who are genetically more at risk have more to gain as the risk is reduced by about 60 per cent.