I’ve been looking lately into the definition of dementia. When caregivers of those with progressive supranuclear palsy (PSP) call me for the first time, I often ask “does your loved one have dementia,” knowing that at least half of those with PSP have dementia as a primary symptom. Often the caregivers will say “no,” and then go on to tell me how their loved one can no longer balance a checkbook, make investment decisions, or make any sort of decisions. Perhaps these caregivers are embarrassed to say that their loved ones are demented. Or perhaps the only kind of dementia they are aware of is Alzheimer’s Disease, and they know their loved ones don’t have that. Or perhaps we are using different definitions or criteria.
The only standard definition of dementia I’m aware of is the DSM IV criteria. (DSM = Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition, published by the American Psychiatric Association, Washington, DC.) According to a University of Alberta website:
“Dementia is a clinical state characterized by loss of function in multiple cognitive domains. The most commonly used criteria for diagnoses of dementia is the DSM-IV. Diagnostic features include: memory impairment and at least one of the following: aphasia, apraxia, agnosia, disturbances in executive functioning. In addition, the cognitive impairments must be severe enough to cause impairment in social and occupational functioning. Importantly, the decline must represent a decline from a previously higher level of functioning. Finally, the diagnosis of dementia should NOT be made if the cognitive deficits occur exclusively during the course of a delirium.”
(Wikipedia definitions: aphasia = loss of the ability to produce and/or comprehend language; apraxia = loss of the ability to execute or carry out learned purposeful movements, despite having the desire and the physical ability to perform the movements; agnosia = loss of knowledge or loss of the ability to recognize objects, persons, sounds, shapes, or smells)
The problem is that there are many different types of dementia (70 or 80 types) and their characterizations are all so different. And, as the abstract below indicates, not all types of dementia have memory impairment.
The Canadian Journal of Neurological Sciences. 2007 Mar;34 Suppl 1:S11-8.
Clinique de mémoire et unité de recherche Alzheimer, CHA Hôpital de I’Enfant-Jésus, Québec, QC, Canada.
In the past two decades there has been a tremendous effort among clinicians and searchers to improve the diagnostic criteria of the dementias on the basis of the differential neurological and neuropsychological profiles. This was an obligatory requirement for clinical trials and the development of treatments. Over the years it became rapidly evident that the cohorts of patients in studies had some degree of heterogeneity, making it difficult to interpret the results of some studies, particularly in the vascular dementias and the mild cognitive impairment (MCI) group. For example, many sub-types of the vascular group were included in clinical trials, such as the cortical strokes, the lacunar states and the diffuse white matter disease cases, and some of the patients might have had also mixed pathology. In addition, the standard DSM IV criteria for dementia no longer represent our present knowledge of the clinical profile of some of the dementias such as vascular dementia (VaD) and fronto-temporal dementia where the memory impairment is not necessarily the first requirement. To improve the validity of clinical trials and eventually help developing more appropriate treatments, we revised the present diagnostic criteria and made recommendations for some changes in the context of the 2nd Canadian Conference on the Development of Antidementia Therapies, held in 2004 and reviewed in the light of the recent literature as of early 2006. It is expected that in the near future, these dementia criteria for clinical trials will have to be revised again in order to include specific subtypes of the dementias as well as biomarkers, structural and functional imaging.
PubMed ID#: 17469675 (see pubmed.gov for the abstract only)