Dementia is the loss of cognitive functioning — thinking, remembering, and reasoning — to such an extent that it interferes with a person's daily life and activities. Some people with dementia cannot control their emotions, and their personalities may change. Dementia ranges in severity from the mildest stage, when it is just beginning to affect a person's functioning, to the most severe stage, when the person must depend completely on others for basic activities of living.
About one-third of all people age 85 or older may have some form of dementia, but it is not a normal part of aging. Many people live into their 90s and beyond without any signs of dementia. Signs and symptoms of dementia result when once-healthy neurons or nerve cells in the brain stop working, lose connections with other brain cells, and die. While everyone loses some neurons as they age, people with dementia experience far greater loss.
People with intellectual and developmental disabilities can also develop dementia as they age, and recognizing their symptoms can be particularly difficult. It’s important to consider a person’s current abilities and to monitor for changes over time that could signal dementia.
The causes of Alzheimer’s and related dementia can vary, depending on the types of brain changes that may be taking place. While research has found that some changes in the brain are linked to certain forms of dementia, in most cases, the underlying causes are unknown. Rare genetic mutations may cause dementia in a relatively small number of people.
Although there is no proven prevention, in general, leading a healthy lifestyle may help reduce risk factors that have been associated with these diseases.