Information about Dementia & Cognitive Decline

Dementia refers to a significant intellectual decline that persists over time and affects several areas of cognition (thinking). Dementia often is not diagnosed until months or even years after its onset. Memory loss is a universal feature of dementia, but other functions are impaired as well, such as abstract thinking and language.

Approximately 1 percent of dementia cases are reversible. In these instances, people may have a physical or psychological condition (such as an operable brain tumor, vitamin B12 deficiency, thyroid disease, alcoholism, or depression) that can be cured with treatment. The most common cause of reversible dementia is a toxic reaction to prescription or over-the-counter medications.

Ask the Doctor about Dementia & Alzheimer's Disease

Q: How are the symptoms of dementia and Alzheimer's disease different?

A: The word "dementia" is a general term describing diseases that cause cognitive impairments resulting in impaired daily function. There are around 75 causes of dementia; the most common is Alzheimer's, which accounts for 60 to 70 percent of dementia cases.

The symptoms of each cause of dementia differ, although there is considerable overlap. Doctors distinguish among causes by recognizing symptom patterns that are relatively unique to each cause. Although the only sure way to determine the existence of Alzheimer's is through an autopsy, diagnosis by an experienced physician is accurate 85 to 90 percent of the time.

While no two cases of dementia or Alzheimer's are exactly alike because symptoms vary between individuals, the patterns are usually recognizable. This allows the diagnosing clinician to provide information about current symptoms and make predictions about future symptoms and the course of the disease.

Many but not all dementias cause memory impairment. In Alzheimer's, it is usually the first of 10 major signs of the disorder that people notice.

Publication Review By: Peter V. Rabins, M.D., M.P.H.

Published: 09 Mar 2011

Last Modified: 23 May 2013