What Is Dementia?

Dementia describes the gradual deterioration of intellectual abilities and behavior that eventually interferes with customary daily living activities, including balancing the checkbook, keeping house, driving your car, involvement in social activities and working. This may also include changes in personality and emotions.

Dementia is caused by ongoing damage to cells in the brain. The brain controls all the functions of the mind and body. Some parts of the brain control memory and language; other parts control movement and coordination.

With dementia, nerve cells in the brain are gradually damaged or destroyed. Why this occurs is not yet clear, but over time, parts of the brain begin to atrophy (shrink). Brain atrophy often starts in the part of the brain that controls memory, reasoning and personality. Other parts of the brain may not be affected until much later in the illness.

Dementia influences all aspects of mind and behavior, including memory, judgment, language, concentration, visual perception, temperament and social interactions. Although dementia symptoms are eventually obvious to everyone, in the early stages special evaluations are necessary to demonstrate the abnormalities.

Dementia is not a single disease, but a set of symptoms and signs related to multiple diseases or brain injuries. Researchers have found as many as 50 causes for dementia, including vascular related causes, kidney and liver disease, thyroid disease, drug and alcohol abuse and vitamin B12 deficiency.

Alzheimer’s disease is the most common form of dementia, affecting about three quarters of all dementia patients. While the symptoms of Alzheimer’s disease are similar to other forms of dementia, the physiological changes in the brain can be very different. 

If you have mild cognitive impairment—slight but persistent memory loss that doesn’t interfere with your activities of daily living—you should talk about those symptoms with your physician.