Dementia and Alzheimer’s Disease: What is the Difference?
In the same way that alcoholism, cocaine addiction, and heroin addiction are different and yet are all addictions, Alzheimer’s disease is a form of dementia. There are many types of dementia, which is a term for a general syndrome in the same way that addiction or cancer are general terms for a family of related syndromes.
The term “dementia” is used to describe a number of conditions that result in a loss of intellectual capacities occurring in the context of clear consciousness (e.g., occurring in the absence of a delirium). Most often the first cognitive domain affected in dementia is memory; however, in some forms of dementia this is not necessarily the case.
The DSM-IV-TR diagnostic criteria for dementia (the diagnostic manual used by mental health care professionals in the United States) consists of memory loss and the loss of one other cognitive domain (e.g., a significant decline in language-related skills, visual-spatial skills, or executive functions such as the ability to sequence events or to think abstractly). This loss of functioning must result in significant distress or impairment in occupational, social, or other areas of the person’s functioning and reflect a significant change from the person’s prior functioning. There are some concerns that these criteria are too liberal sometimes resulting in inappropriate dementia diagnoses and more stringent criteria have been proposed. In any event, a diagnosis of dementia should be made after a formal evaluation that includes a full medical workup (preferably by a neurologist) and a neuropsychological evaluation.
The memory loss occurring in dementia differs qualitatively from normal memory loss associated with aging and requires a formal assessment that is often overlooked by family physicians. In addition, there are a number of medical conditions that can mimic dementia such as thyroid conditions, low vitamin B12 levels, or even depression and these will need to be ruled out as well. The medical workup will often consist of an interview, history, medical examination, laboratory tests, neuro-imaging, and formal neuropsychological testing (which tests cognitive faculties). While neuro-imaging techniques such as CT or MRI brain scans assist in the diagnosis of dementia, these alone cannot be used to diagnose dementia.
Dementia can be permanent or reversible, have a sudden or gradual onset, or it can progress quickly, slowly, or remain relatively static depending on its cause. Potential causes of dementia are too numerous to fully list here but include Alzheimer’s Disease, Stroke, other vascular conditions, psychiatric disorders, tumors, metabolic disturbances, movement disorders such as Parkinson’s disease, infections such as HIV, alcoholism or other substance abuse, genetic disorders, certain types of organ failure, head trauma, and a host of other medical conditions.
The prevalence rate of dementia is about five percent in the general population older than 65 years-old; however, most sources typically report that the prevalence doubles for every decade of life after age 65 and the prevalence rates for those 85 and older is between 20 to 40 percent. The prevalence rate has been quoted as high as 50 percent or more in chronic care facilities for the elderly.
Risk factors for contracting dementia will vary somewhat by dementia type, but there are some general risk factors. As discussed above, the risk of contracting most any form of dementia increases with age. A second significant risk factor is level of education. Interestingly, people with lower levels of education are at a higher risk to develop dementia. This has brought forth speculation about “cognitive reserve” as a potential protective factor against dementia; people with higher levels of education have developed more neuronal connections and therefore are at lesser risk to develop dementia or develop it later than their less-educated cohorts. Having a first-degree relative with dementia increases your risk of developing dementia and having more than one first-degree relative significantly increases this risk. The risk for developing any form of dementia also slightly increases if you are female (but this may be a statistical artifact as females still live longer than males and males have higher rates of vascular dementia), whether or not you smoke, and if you have a history of head trauma that produced a period of unconsciousness.
Alzheimer’s disease accounts for most cases of dementia (50-60 percent), followed by vascular dementia (anywhere from 15-30 percent). About 10-15 percent of cases have co-occurring Alzheimer’s disease and vascular dementia. Other common forms of dementia include Lewy body dementia (which according to some sources is more prevalent than vascular dementia) and dementia associated with Parkinson’s disease.
