Dr Marilyn Glenville explained: "People with Alzheimer’s [a form of dementia] have been found to have a shortage of the neurotransmitter acetylcholine." The neurotransmitter is said to be "critical" for a healthy brain.

"Plaques tend to spread through the Corte in a predictable pattern as Alzheimer's disease progresses.".

In the earliest stages of the disease, before symptoms can be detected, plaques form in areas of the brain involved in learning and memory, as well as thinking and planning.

When the disease progresses moderately, those affected begin to experience problems with memory and thinking skills that interfere with work or social life.

"Many people with Alzheimer's are first diagnosed in these stages," the charity said.

As Alzheimer's progresses even further, people may experience changes in personality.