Alzheimer’s disease Alzheimer’s disease is the most common type of dementia. Alzheimer’s disease, named after the doctor who first described it (Alois Alzheimer). It’s found in more than half of people diagnosed with dementia. It is a physical disease causing permanent damage to individual brain cells, due to the build-up of proteins causing Plaques and Tangles. The numbers of damaged cells gradually increase over time, so the brain starts to function less and less well. People with Alzheimer’s also have a shortage of some important chemicals in their brain. These chemicals help to transmit messages around the brain, so when there is a shortage the signals are not transmitted as effectively. It may begin slowly, and the decline can happen over a number of years. It usually affects short–term memory first. Gradually, everyday tasks become more and more difficult. No two people are the same.