What is Alzheimer’s disease?


Alzheimer’s disease is marked by a progressive degeneration of brain tissue, causing dementia. Eventually, people suffering from Alzheimer’s disease lose the ability to think, reason and co-ordinate movement, becoming incapacitated over the course of five to eight years. 

This incurable brain disease was named after the German physician Alois Alzheimer, who identified it in 1907.

The disease is characterised by a progressive degeneration of brain tissue. It primarily affects people over the age of 65 and in such cases, it is known as late-onset Alzheimer’s disease.

The disease has also been reported among people in their 50s, 40s. It is rarely diagnosed in people in their thirties and is called early-onset Alzheimer’s. Nearly all people with Down syndrome will develop this disease if they live into their 40s.


The prevalence of Alzheimer's disease is closely linked to age and dramatically increases with age. The risk for developing Alzheimer’s disease or a related dementia doubles every five years from the age of 60.

It affects 10% of all persons older than 65 years and 50% of those older than 85 years.

At age 60, the risk is approximately 1 in a hundred, by 65 years 1 in 50, 70 years 1 in 20, etc. By 85 and older, approximately two out of every five people have some form of dementia.

Increasing age is the main risk factor for Alzheimer's disease. Other risk factors include a family history of dementia and previous head trauma.

Read more: 

Treating Alzheimer's disease

Symptoms of Alzheimer's disease 

Causes of Alzheimer's disease

(Updated and reviewed by Dr Michael S. Mason, MB ChB, FC Psych (South Africa), Consultant Psychiatrist in private practice, Panorama Psychiatry and Memory Clinic, Cape Town March 2015.)

(Previously reviewed by Dr Frans Hugo, MBChB, M.Med Psychiatry)


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