Many a patient (or the family) has asked, "What is Alzheimer's disease, and what makes it different from dementia?"
The term dementia refers to a health condition marked by a progressive loss of cognitive or intellectual abilities. There are many types of dementia, arising from different causes, the most common of which is Alzheimer's disease.
According to the National Institutes of Health, Alzheimer's disease comprises 60% of all dementia cases, while vascular dementia accounts for about 25%, with the remaining 15% coming from the other types.
The renowned neurologist, M. Marsel-Mesulam of Northwestern University, has formulated a precise definition of dementia. He describes a "progressive deterioration in intellectual abilities and/or comportment, which eventually results in a restriction of customary daily living activities."
Progressive means the changes occur over longer periods of time. A sudden decline in intellectual abilities is not associated with dementia. While not a specific disease, dementia describes a collection of symptoms that can be caused by various disorders that affect the brain.
A person with Alzheimer's disease will initially experience memory loss and confusion, then a gradual but steady deterioration in intellectual abilities.
Intellectual abilities refer to cognitive functions that may be separately impacted by dementia, such as memory (sensory, short-term, and long-term), language, spatial reasoning, and executive functions (planning ahead, evaluating future consequences, and making decisions).
Comportment is behavior during social interactions, which requires normal functioning of the brain's frontal lobes. A common type of dementia (not Alzheimer's) initially affects a person's social reasoning abilities, and consequently the social behavior.
Daily living activities usually refer to one's ability to perform self care functions, drive a car, balance a checking account, do household chores, and be socially active. While a person may be unable to work out complicated mental problems, he or she won't be labeled demented if still able to carry out ordinary activities of daily living.
Dementia is not a necessary consequence of aging. It is caused by a variety of disorders and diseases that damage the brain.
Alzheimer's disease is the leading cause of dementia. In Alzheimer's disease, the brain slowly degenerates as bundles of fibrous tissue get tangled (called neurofibrillary tangles) and abnormal masses of material are formed (called amyloid or neuritic plaques). These formations lead to the destruction of healthy brain cells (neurons). They usually cluster in the parts of the brain that control memory function.
Alzheimer's disease is categorized into familial and sporadic. The familial variety, a genetically transmitted form of Alzheimer's disease, is rare and accounts for only about 5% of Alzheimer's disease cases. For this subtype, disease onset typically occurs before the age of 65.
The bulk of Alzheimer's disease cases, 95%, belongs to the sporadic category, which means the disease occurs on a random basis in the population, although family history is one of the risk factors. Current research indicates that development of the disease is not linked to any dietary habits, personality type, or type of work.
In conclusion, dementia is a medical condition characterized by gradual loss of one's mind, while Alzheimer's disease is one of the many disorders that eventually results in dementia.