Major neurocognitive disorder (NCD), known previously as dementia, is a decline in mental ability severe enough to interfere with independence and daily life.

This term was introduced when the American Psychiatric Association (APA) released the fifth edition of its Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Dementia is the loss of cognitive functioning— the ability to think, remember, problem solve or reason— to such an extent that it interferes with a person’s daily life and activities. The word “dementia” is related to a Latin word for “mad,” or “insane.” Because of this, the introduction of the term neurocognitive disorder attempts to help reduce the stigma associated with both the word dementia and the conditions that it refers to. That said, because the word dementia is in common use and is easily understood by everyone, it will likely remain in use.

Neurocognitive disorders range 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 daily living. Functions affected include memory, language skills, visual perception, problem solving, self-management, and the ability to focus and pay attention. Some people with dementia cannot control their emotions, and their personalities may change.

While dementia is more common with advanced age (as many as half of all people age 85 or older may have some form of dementia), it is not normal part of aging. Many people live into their 90s and beyond without any signs of dementia. Prevalence of dementia increases exponentially with increasing age, and doubles every five years of age after age 65. In higher income countries such as the U.S., prevalence is 5–10% in those aged 65+ years, usually greater among women than among men, in large part because women live longer than men. Within the U.S., higher prevalence has been reported in African American and Latino/Hispanic populations than in White non-Hispanic populations.