By Ania Lichtarowicz BBC science correspondent

Having a healthy diet, exercising and not being overweight can not only reduce the risk of developing heart disease, but may also protect against Alzheimer's, new research claims.

The research is being presented to 4,000 scientists at the six-day Alzheimer's Association conference in Stockholm, Sweden, from Saturday, the largest meeting dedicated to the disease.

So far doctors have been unsure about what causes Alzheimer's disease - although, both genetic and environmental influences are thought to play a part.

Now researchers believe they may have linked certain risk factors which are known to cause heart disease to the neurological condition.

12 million cases

Alzheimer's is one of several disorders in which brain cells are gradually lost.

Initially, sufferers find it hard to form new memories and cannot remember recent events.

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As the disease progresses, their long-term memory is also affected and it can be a cause of death.

It is estimated there are about 12 million cases of Alzheimer's worldwide, but this figure is increasing so fast that more than 22 million people will be affected by 2025, experts say.

The research will bolster support for cholesterol-lowering drugs

Scientists still do not know exactly why and how the disease develops but the biggest risk is simply age: Alzheimer's cases double with every five years of age between 65 and 85.

At the Stockholm meeting, scientists will claim lack of exercise, excess weight, high cholesterol and blood pressure can all increase the risk of developing the disease. Even diabetes appears to have an effect.

Several studies to be presented will indicate that people may be able to reduce the risk by taking early steps to treat high blood pressure.

Vitamin link

Three other studies will bolster evidence that taking cholesterol-lowering drugs will also lower the risk of developing the condition.

As Alzheimer's may start developing 20 or 30 years before the first symptoms appear, doctors say that keeping healthy in younger life is vital to ensure healthy ageing.

Two studies published in the Journal of the American Medical Association last month found people who ate foods rich in antioxidants such as vitamin E and C were less likely to develop Alzheimer's.

Antioxidants are important because they combat the body's free radicals - chemicals which are often highly reactive and can damage cells.