The study by independent market analyst Datamonitor found that large numbers of people who may have developed Alzheimer's mistakenly believe there is nothing that can be done to help them.

Datamonitor is calling on drug companies to raise awareness both of the disease and available therapies.

The number of people with Alzheimer's disease is set to triple in the next 30-40 years as the average age of the global population soars.

Datamonitor, which surveyed 220 doctors across the world, says that one in 10 people over the age of 60 already shows signs of the disease - but only one in three are receiving any treatment.

Effective treatments

Ben Greener, a neurology analyst at Datamonitor, told BBC News Online: "Many people view the symptoms of Alzheimer's disease as a normal process of ageing, whereas it is not.

Three drugs - Aricept, Exelon and Reminyl - have all been shown to be effective treatments for mild to moderate forms of Alzheimer's.

Many doctors are lukewarm about the medications as they feel that they simply delay the onset of symptoms and are not effective in the long-term.

However, research has shown that the drugs are far more effective if administered in the early stages of the disease.

Datamonitor says that if they were more widely used from the outset, the quality of life for both the patient and the care-giver could be greatly improved.

Quality of life

Dr Richard Harvey, director of research at the Alzheimer's Society, said that elderly people with the disease were "at the bottom of the pile" when it came to health resources.

"They cannot assert their own rights, and their carers are often too tired and burdened to stand up for them," he said.

"For such a serious and damaging disease, it is a scandal to hear that less than half of people with dementia seek a diagnosis, and that only one in three receive any form of treatment.

"While treatments don't work for everyone, and the effects are not permanent, they nevertheless have a real impact on people's quality of life."

Rebecca Wood, chief executive of the Alzheimer's Research Trust, said: "It is very important that people are aware of the three relatively new drugs which are available for the treatment of Alzheimer's in the mild to moderate stages of the disease."

The Alzheimer's Research Trust is funding a major project in early diagnosis which should in future mean even more people can benefit from this help.