Dr Dougal claims that only ten minutes under the hat a day is enough to have an effect.

"Currently all you can do with dementia is to slow down the rate of decay - this new process will not only stop that rate of decay but partially reverse it," he said.

Low level infra-red red is thought to stimulate the growth of cells of all types of tissue and encourage their repair. It is able to penetrate the skin and even get through the skull.

"The implications of this research at Sunderland are enormous - so much so that in the future we could be able to affect and change the rate at which our bodies age," he said.

"We age because our cells lose the desire to regenerate and repair themselves. This ultimately results in cell death and decline of the organ functions - for the brain resulting in memory decay and deterioration in general intellectual performance.

The test identifies changes in a handful of proteins that cells use to convey messages to one another.

The US researchers found it could indicate who had Alzheimer's, as well as who was likely to develop the condition, with 90% accuracy.

The work, led by Stanford University, features in Nature Medicine.

One of the most distressing aspects of Alzheimer's disease is the difficulty in determining whether mild memory problems are the beginning of an inevitable mental decline.

More than 5 million Americans are living with Alzheimer's disease, a 10 percent increase since the last Alzheimer's Association estimate five years ago and a count that supports the long-forecast dementia epidemic as the population grays.

Age is the biggest risk factor, and the report to be released Tuesday shows the nation is on track for skyrocketing Alzheimer's once the baby boomers start turning 65 in 2011. Already, one in eight people 65 and older have the mind-destroying illness, and nearly one in two people over 85.

Unless scientists discover a way to delay Alzheimer's brain attack, some 7.7 million people are expected to have the disease by 2030, the report says. By 2050, that toll could reach 16 million.

Why? Ironically, in fighting heart disease, cancer and other diseases, "we're keeping people alive so they can live long enough to get Alzheimer's disease," explains association vice president Steve McConnell.

The test zeroes in on two forms of an enzyme involved in the degradation of amyloid, the protein that accumulates in the brain of someone with Alzheimer's, said Alkon, scientific director of the Blanchette Rockefeller Neurosciences Institute at the West Virginia University Health Sciences Center.

The presence of Alzheimer's disease is indicated by a steep imbalance in the ratio of the two forms of the enzyme, MAP kinase Erk, in skin cells that are exposed to bradykinin, an inflammation-related molecule, Alkon said. That imbalance is not seen in cells of people without dementia or those with other forms of dementia, he said.

The test produced good results when run on 60 tissue samples: 30 from a tissue bank, 30 from autopsy samples of people diagnosed with Alzheimer's disease, Alkon said.

"We have seen a correlation with the duration of the disease," he said. "The earlier it is done in the course of the disease, the larger is the abnormality."

During the trial, a brief pulse of infrared light into the eyes of four mice with Alzheimer's and four without accurately identified which had the condition.

Dr Goldstein and his team envisage the test could be used to detect the disease at its earliest stages as well as to track disease progression and monitor how people respond to Alzheimer's treatments.

Currently there is no simple test to make a diagnosis of dementia and it can only be confirmed with certainty by looking at someone's brain in a post-mortem examination.

The scientists believe the technology, known as quasi-elastic light scattering, may detect the very earliest stages of amyloid deposits in the lens, even when they appear completely clear to the naked eye.

In their analysis, Park and his colleagues found that the bank tellers, clergy, aircraft mechanics and hairdressers had highest odds of dying from Alzheimer's disease. For Parkinson's disease, the highest risks were among biological scientists, teachers, clergy members and other religious workers.

The risk of death from presenile dementia - a form of dementia that arises before the age of 65 - was greatest among dentists, graders and sorters in industries other than agriculture and, again, clergy.

Veterinarians, hairdressers and graders and sorters had the highest risks of dying from motor neuron disease, the most common form of which is amyotrophic lateral sclerosis, also known as Lou Gehrig's disease - an invariably fatal degeneration of the central nervous system that causes muscle wasting and paralysis.

The findings, based on death records from 22 states for the years 1992 to 1998, are published in the American Journal of Industrial Medicine.

Astrocytes produce fat-like lipid neurons used to create their outer membranes and they also produce glutamate, the most abundant neurotransmitter in the nervous system and one of the most important chemical messengers in the brain.

Recent experiments, however, revealed that astrocytes form connections with blood vessels and control the flow of nutrients, including oxygen, to neurons. When brain activity increases, neurons trigger astrocytes to release calcium, which in turn affects other chemical messengers that can cause blood vessels to either dilate or contract.

The classical symptoms of memory loss and dementia associated with Alzheimer's are the result of neurons dying over a period of years. Brain scans of Alzheimer's patients show decreased blood flow to critical parts of the brain, and doctors have always assumed that this was because there was less of a demand for blood because there were fewer neurons to feed.

The new result could mean that Alzheimer's affects mainly astrocytes and not neurons and that blood flow to the brain is not decreased because the neurons are dying, but that the neurons are dying because there is decreased blood flow.

"It may be that for whatever reason, astrocytes are not doing their job properly, and then blood flow decreases," Nedergaard said. "This could lead to the death of the neurons, which would starve from a lack of nutrients, since the neurons depend on the astrocytes for their survival."

Still, the discovery may provide leads to scientists searching for therapies to at least delay the onset of the degenerative brain disease. It already affects 4.5 million people in the U.S. and is predicted to strike 14 million by 2050 as the population ages.

Moreover, researchers are honing in on lifestyle choices that may help protect the brain in the first place.

"It's exciting that we can even talk about prevention," said William Thies, scientific director of the Alzheimer's Association. He noted that just 10 years ago there was hardly any research into that possibility.