Dementia and its types

­Dementia can be defined as a loss of mental functions that is both acquired and persistent and affects multiple cognitive and behavioral domains (Mendez & Cummings, 2003). By this definition, some decline from a formerly higher level has occurred (i.e., “loss”). This loss is primarily due to mental abilities, rather than physical disabilities (e.g., hemiparalysis). This loss is acquired, rather than lifelong (e.g., mental retardation). This loss is persistent, rather than transitory (e.g., delirium). And this loss affects multiple spheres, rather than one circumscribed domain (e.g., aphasia, amnestic disorder). Despite the specifics of this definition, dementia remains a vague concept that varies greatly in its presentation and causes.


  • Alzheimer’s Disease (AD)
  • Vascular Dementia
  • Mixed Dementia
  • Frontotemporal Dementia (FTD)
  • Dementia With Lewy Bodies
  • Reversible “Dementias”

Alzheimer’s Disease (AD)

Diagnostic Criteria and Prevalence

AD is the most common type of dementia, with prevalence rates as high as 10% in community-based samples (Fitzpatrick et al., 2004) and 68% in memory disorder clinics (Paulino Ramirez Diaz et al., 2005). Although a definite diagnosis still requires a post-mortem neuropathological examination of brain tissue for the hallmark signs of neuritic plaques and neurofibrillary tangles, two pre-mortem sets of diagnostic criteria are widely employed in clinical and research settings. Clinically, the diagnosis can be made with evidence of memory impairment plus at least one other cognitive disturbance (aphasia, apraxia, agnosia, or executive dysfunction), a significant decline from a premorbid level, and a gradual onset with the progressive course (American Psychiatric Association, 2000). The National Institute of Neurological and Communicative Disorders and Stroke and Alzheimer’s Disease and Related Disorders Association (NINCDS-ADRDA) criteria for probable AD (McKhann et al., 1984), however, are more commonly used in research studies.

Vascular Dementia

Diagnostic Criteria and Prevalence

Occurring less frequently than AD, the prevalence of vascular dementia (VaD) is approximately 2–4% in community elders (Fitzpatrick et al., 2004) and 10% in patients seen in specialty clinics (Paulino Ramirez Diaz et al., 2005). Despite its relatively smaller numbers, it is considerably more heterogeneous in its presentation and definition than AD. VaD has also been called multi-infarct dementia and could be due to either hemorrhagic or ischemic events affecting large or small blood vessels. Because the clinical diagnosis of VaD in the APA (2000) Diagnostic and Statistical Manual of Mental Disorders, 4th ed., text revision (DSM–IV-TR) is quite similar to that of AD, other diagnostic criteria have been developed to further separate these two common types of dementia. Perhaps most widely used in research settings is the National Institute of Neurological Disorders and Stroke—Association Internationale pour la Recherche et l’Enseignement en Neurosciences (NINDS-AIREN) criteria (Roman et al., 1993), which provides criteria for possible and probable VaD .

Mixed Dementia

In addition to AD and VaD in their pure forms, the combination of these two conditions often referred to as mixed dementia, also appear to be quite common. Across several studies, from 25–50% of patients with AD also have sufficient vascular pathology to be deemed VaD (Langa, Foster, & Larson, 2004; Zekry, Hauw, & Gold, 2002). Neuropsychological and neuroimaging comparisons between AD, VaD, and mixed dementia tend to show that the latter two conditions are most similar (Zekry et al., 2002). Whether these conditions are truly separate and warrant distinct diagnostic criteria is unclear. It is clear, however, that multiple types of dementia pathology can co-occur, with each leading to its own type of deficits and impairments.

Frontotemporal Dementia (FTD)

Diagnostic Criteria and Prevalence

Perhaps the third most common type of dementia, FTD is one of several dementias that falls under the spectrum of Frontotemporal Lobar Degeneration (e.g., Pick’s disease, primary progressive aphasia, corticobasal degeneration, motor neuron disease). About 2–5% of memory disorder patients will be diagnosed with FTD (Lund & Manchester, 1994), and it is frequently misdiagnosed as AD. Consensus clinical criteria for FTD are presented in Table 19.3 (Neary et al., 1998), although additional criteria are also available (Lund & Manchester, 1994).

Dementia With Lewy Bodies

Diagnostic Criteria and Prevalence

Although the prevalence of Lewy body inclusions in dementia cases is relatively common, the actual prevalence of dementia with Lewy bodies (DLB) remains unclear (Zaccai, McCracken, & Brayne, 2005). The application of the formal diagnostic criteria (McKeith et al., 1996), however, might begin to clarify this picture. Nonetheless, this disorder has several striking features that make DLB a “high profile” dementia.

Reversible “Dementias”

Diagnostic Criteria and Prevalence

There are many medical conditions that can lead to the cognitive and behavioral disturbances of dementia (e.g., vitamin deficiencies, substance abuse, endocrine pathologies, normal pressure hydrocephalus), and many of these dementias can be reversed with proper medical care (Mendez & Cummings, 2003). One of the more prevalent reversible dementias that falls within this category is depression-associated dementia. Separate diagnostic criteria have not yet been developed for depression-associated dementia, but the symptoms of major depressive disorder include depressed mood, anhedonia, changes in weight/ appetite, changes in sleep, feelings of worthlessness/guilt, poor concentration, and thoughts of death/dying (APA, 2000).

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One thought on “Dementia and its types

  • September 21, 2021 at 2:00 am

    Fantastic blog! Do you have any recommendations for aspiring writers? I’m hoping to start my own blog soon but I’m a little lost on everything. Would you advise starting with a free platform like WordPress or go for a paid option? There are so many options out there that I’m totally overwhelmed .. Any ideas? Many thanks!


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