Many people are under the impression that Alzheimer Disease (AD) and dementia are different conditions. In fact, AD is a type of dementia. In addition to AD, dementia also includes types such as vascular dementia, frontotemporal dementia, and dementia with Lewy bodies.
Many people, particularly those who are very old, have mixed dementia or dementia that is caused by more than one kind of brain disease.
AD is currently considered the most common kind of dementia. Researchers estimate that as many as 5.5 million people living in the United States have this type of dementia.*
Although scientists have found various genetic and environmental factors that may increase the likelihood of having AD, age is the most important risk factor.
In the United States, about 1 out of every 20 men and women between the ages of 65 and 74 have AD.* The frequency for this disease nearly doubles every five years beyond age 65. Researchers believe that nearly half of all people older than 85 may be in various stages of the disease.
Vascular dementia, accounting for 12 to 20 percent of all dementias, is the second most common age-related dementia.* Unlike the gradual progression of AD, the onset of vascular dementia symptoms is often abrupt and may occur when a heart attack or a stroke dramatically reduces blood flow to or through the brain.
Vascular dementia can also have a slow progression. This happens when the accumulative damage of transient ischemic attacks - often called TIAs - causes many small areas of brain damage and, eventually, noticeable symptoms. The descriptive name “multi-infarct dementia” is the term healthcare providers use to describe this kind of vascular dementia. Multi-infarct dementia is the most common type of vascular dementia.
Each type of dementia has specific signs and symptoms. For example, memory loss, confusion, and difficulty in performing what was once familiar and easy tasks are early symptoms of AD. In contrast, the early symptoms of frontotemporal lobe degeneration (FTD) are poor coordination, tremors, and difficulty in using and understanding written and spoken language. Memory loss is another aspect of FTD but occurs much later in the course of the disease. Ultimately, however, memory loss is a symptom that all forms of dementia have in common.
Examples of other types of dementia include dementia resulting from Traumatic Brain Injury (TBD); Wernicke-Korsakoff Syndrome (WKS); Normal Pressure Hydrocephalus (NPH); Chronic Traumatic Encephalopathy (CTE); Creutzfeldt-Jakob Disease (CJD), and others.
* https://www.alz.org/facts/downloads/facts_figures_2015.pdf (accessed May 5, 2016)
Janet Yagoda Shagam, Ph.D., is a freelance medical and science writer and the author of “An Unintended Journey: A Caregiver's Guide to Dementia.” Available through Amazon.
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