Introduction
Theoretical concepts in medicine reflect the knowledge and thinking of a particular time and are subject to change as the field advances. For example, the concepts of “neurosis” and “psychosis” have been dismissed from psychiatric classification because these constructs imply etiological assumptions which have been refuted by research, and because these constructs suggest a dichotomy which is no longer helpful as a fundamental organizing principle (Beer, Reference Beer1996). Similarly, the usefulness and appropriateness of the concept of dementia is called into question by progress in research. In specialized units such as memory clinics patients may receive a diagnosis of dementia at a stage of their illness where they still retain much of their intellectual capacity and functioning on everyday activities. Refined neuropsychological assessments in conjunction with laboratory tests and imaging technologies enable physicians to identify neurodegenerative brain diseases before they manifest as dementia. Furthermore, a number of brain diseases are being recognized as important causes of cognitive deterioration for which the current concept of dementia is not a good fit, because it is shaped by the subtype of Alzheimer's disease. In the present paper we discuss whether, in the light of these developments, dementia is still a valuable concept or whether it should now be abandoned.
A brief history of the concept of dementia
Intellectual decline in old age was known in antiquity and was regarded as a social problem rather than a medical matter (Berrios, Reference Berrios1996). According to the statesman Solon and the philosopher Plato, mentally impaired elderly individuals are incapable of making a will and cannot be held accountable for unlawful acts, but are also not eligible for official positions. Thus, from the earliest times, dementia has been associated with reduced civic and legal competence on the one hand, but with entitlement to support and protection on the other. The term “dementia” (Latin: de mens), which literally means “absence of mind”, is said to have been coined by Aulus Cornelius Celsus in the first century AD and was included in the catalog of mental disorders by Claudius Galenus (AD 129–199). The cognition-centered concept of dementia dates back to Cosin who described it in 1592 as a state of memory weakness which not only involves recent events but also previous knowledge, including the meaning of words and the person's own name. In the nineteenth century, William Cullen defined dementia as a combined impairment of memory, particularly pertaining to recent events, and of judgment. As in the Roman era, dementia carried clear social and legal connotations. It was held to reduce the abilities of patients to enter into contracts, to make a will, to handle their own affairs, to be appointed to public office, and to be criminally responsible (Berrios, Reference Berrios1987). A medical description of dementia that approximates contemporary definitions was provided by the influential French psychiatrist Philippe Pinel (1745–1826). According to him, dementia is characterized by the inability to form associations between ideas, which leads to aimless activity, nonsensical behavior, superficial emotions, memory disorder, impaired perception of objects, reduced judgment, and word-finding difficulty. Psychiatrists in German-speaking countries at that time broadly defined dementia as a combination of impairments in judgment and memory. Some writers emphasized the deterioration of thinking (Christoph Hoffbauer, 1766–1827; Ernst von Feuchtersleben, 1806–1849) while others highlighted the memory component (Wilhelm Griesinger, 1817–1868). Nineteenth-century British psychiatrists, including James Pritchard (1786–1848), considered impairment of memory to be the primary feature of dementia (Berrios and Hodges, Reference Berrios and Hodges2000). Until the end of the nineteenth century, the concept and the term of dementia were congruent, both referring to a state of acquired intellectual deterioration which significantly interferes with an individual's personal, social and occupational roles.
The transformation of the concept of dementia in psychiatric classification
At the beginning of the twentieth century the distinction between mental disorders caused by identifiable brain diseases and others that lacked a recognizable physical cause became an important issue in psychiatry. For the former category, the German psychiatrist Emanuel Mendel introduced the term “organic” (Mendel, Reference Mendel1902). Attempts were subsequently made to identify symptom patterns within the group of organic mental disorders that were specific to underlying brain diseases. The Swiss psychiatrist Eugen Bleuler contributed the observation that chronic lesions which affect extended areas of the brain are associated with a stereotyped cluster of psychopathological symptoms. He found this peculiar complex of symptoms to be distinct from other organic syndromes such as delirium or amnesia in that it involves multiple domains of cognition including memory, attention, orientation and reasoning but is not associated with clouding of consciousness (Bleuler, Reference Bleuler1916). Bleuler considered this symptom cluster to be a basic form of mental illness, but he felt unable to find an appropriate general term for it. As a preliminary label he chose “psycho-organic syndrome”, and explicitly avoided the term “dementia” because this would only have covered the severe forms of the syndrome. It is important to note that within the boundaries of its definition, Bleuler's psycho-organic syndrome shows considerable variability. The pattern of cognitive deficits and the relation between cognitive and behavioral symptoms are primarily determined by the localization and dissemination of disease (Huber, Reference Huber, Kisker, Meyer, Müller and Strömgren1972), and the syndrome can occur at different levels of severity, from mild to severe.
Consistent with medical tradition, the term “dementia” was used as a descriptor of the severe part of this spectrum in the first two generations of the operational psychiatric classification systems ICD-8 and ICD-9 (World Health Organization, 1978) and DSM-I (American Psychiatric Association, 1952) and DSM-II (American Psychiatric Association, 1968). In the third revision of the DSM (American Psychiatric Association, 1987), however, two major changes were introduced to the concept of dementia. It was expanded to include forms of intellectual impairment which show the typical symptom complex of the diagnostic category at a lesser degree of severity, provided there is some impact on activities of daily living. These are mental states which Bleuler had exempted from his label of “dementia”.
On the other hand, the spectrum of cognitive patterns was narrowed to a memory-prominent variant which is typical for dementia in Alzheimer's disease (AD) but not for intellectual decline of many other etiologies, including cerebrovascular disease, frontotemporal degeneration or subcortical lesions (Derouesné, Reference Derouesné2003). Similar to the DSM-III, the definition of dementia in the ICD-10, released in 1994, requires disturbance of memory and encompasses mild degrees of intellectual impairment, provided they interfere with activities of daily living (World Health Organization, 2007).
The transformation of the concept of dementia in psychiatric classification has two major consequences. First, there is a mismatch between the literal meaning of dementia (absence of mind) and the broad range of mental states which are encompassed by the theoretical concept. Individuals can be allocated to the diagnostic category of dementia because they exhibit cognitive deficits and limitations on activities of daily living, but yet have retained much of their intellectual capacity, and are neither helpless nor dependent on others. Secondly, in its present operationalization, the concept imperfectly captures subtypes which do not feature cognitive decline in general, or memory impairment in particular.
The role of the concept for diagnosis
In essence, the concept of dementia covers those chronic disorders which either affect large parts of the brain or areas of strategic importance that are associated with a particular pattern of psychopathological symptoms. The precise distribution of cognitive deficits and behavioral change depends on the localization of the underlying brain disease, but the pattern is sufficiently typical to allow a differentiation between age-associated cognitive decline (O'Connor et al., Reference O'Connor1996) and syndromes such as delirium (Laurila et al., Reference Laurila2004), amnesia, aphasia or apraxia, which arise from acute or focal brain diseases. The symptom cluster includes a decline from a previous level of memory and other cognitive domains which interferes with the subject's usual activities of daily living, and it encompasses alterations of emotional and social behavior, all occurring in the context of clear consciousness. The current definition of dementia thus incorporates a qualitative and a quantitative component. The qualitative part is the multifaceted pattern of psychopathological abnormalities, indicating either widespread or strategically positioned brain damage. The quantitative component is the sustained impairment of activities of daily living, which implies that the underlying pathology has exhausted the compensatory capacity of the brain and renders recovery unlikely though not impossible. The quantitative criterion thus limits the list of possible causes to chronic and irreversible brain diseases, with few exceptions. On the other hand, it excludes states of “mild” cognitive impairment (Winblad et al., Reference Winblad2004), which may arise from the same brain pathologies and can exhibit similar psychopathological symptoms, although with fewer functional consequences. Both the qualitative and the quantitative features of the concept of dementia are therefore a significant barrier to the early identification of progressive brain diseases.
Owing to increased public awareness of cognitive problems in old age, more people seek – or are brought to – diagnostic evaluation at an early stage of cognitive decline when they still have available much of their intellectual capacity and functional competence. Applying the label of dementia to these individuals may raise anxiety, anger or frustration (Sachdev, Reference Sachdev2000). It also causes discomfort and reluctance in physicians when establishing and disclosing the diagnosis (Burns and Iliffe, Reference Burns and Iliffe2009).
According to current clinical diagnostic criteria the presence of dementia is a prerequisite for the identification of the underlying etiology. This logic of the diagnostic procedure has been explicitly formulated for AD (McKhann et al., Reference McKhann1984; American Psychiatric Association, 2000; World Health Organization, 2007), cerebrovascular disease (Román et al. Reference Román1993), frontotemporal degeneration (McKhann et al., Reference McKhann2001), and dementia with Lewy bodies (McKeith et al., Reference McKeith1996). In research settings, the role of dementia for diagnosis will probably be modified by the development of biological indicators for brain pathologies. Presently, such markers are only available for AD. They include biochemical alterations in the cerebrospinal fluid (Hansson et al., Reference Hansson2006), specific patterns of reduced glucose metabolism on 18F-fluorodeoxyglucose positron emission tomography (Mosconi, Reference Mosconi2005), and increased amyloid beta deposition (Klunk and Mathis, Reference Klunk and Mathis2008). Such novel diagnostic procedures may allow clinicians to identify neurodegenerative processes independently of their clinical manifestation, and thus uncouple etiological diagnosis from syndromal diagnosis (Dubois et al., Reference Dubois2007). The presence of dementia would then denote a stage of the disorder at which symptoms have become so severe that activities of daily living are significantly compromised. The validity of biological indicators remains to be demonstrated. Even if proven to be sufficiently accurate, they are unlikely to play a role in primary care where most patients with dementia are being diagnosed and treated.
Since many cognitive abilities and behaviors are sub-served by specific brain areas (Kipps and Hodges, Reference Kipps and Hodges2006), impairment of these functions provides cues for the identification of the underlying pathology. The potential of the psychopathological diversity of dementia as a guide to differential diagnosis is constrained, however, by the current definition of the syndrome: it is modeled after AD, over-emphasizes the impairment of memory, and inadequately covers the frontal and subcortical variants of the syndrome (Derouesné, Reference Derouesné2003; O'Brien et al., Reference O'Brien2003; Lautenschlager and Förstl, Reference Lautenschlager and Förstl2007).
The role of the concept for patient management
Dementia involves deficits in multiple cognitive domains including memory. It is not a pure cognitive syndrome, since changes of affect and social behavior are key features (Burns, Reference Burns2009). As a consequence of the profound and pervasive changes in intellectual ability and behavior, affected individuals cannot maintain their premorbid level of functioning and personal autonomy, are unable to fulfill their previous social or occupational roles, and require variable degrees of assistance or supervision. With the rare exception of reversible causes (Clarfield, Reference Clarfield2003), patients must cope with permanent or even progressive disability. Accordingly, the management of dementia is a complex task and involves several different kinds of interventions. These need to be integrated in a collaborative system of care and include the patient's family members or other carers (Hogan et al., Reference Hogan2008). Dementia is the prerequisite for prescription of the specific pharmacological treatments that are currently available (Christensen and White, Reference Christensen and White2007) and, in some countries, a prerequisite for government subsidy schemes. On the other hand, this implies that patients who suffer from cognitive and behavioral deterioration below the threshold of dementia are not entitled to treatment and support. Limitation of functional abilities, reduced personal autonomy, and behavioral changes can provide an indication for and justify the reimbursement of non-pharmacological interventions such as occupational therapy or physiotherapy. For the disease-modifying treatments that are under development, a diagnosis of dementia will not be the only and most appropriate access to pharmacological intervention. Strategies which effectively slow down the progression of neurodegenerative brain diseases should be used in minimally impaired patients with the objective of preventing or delaying severe intellectual and functional deterioration (Sano et al., Reference Sano2008).
The role of the concept in public health
In the context of public health, dementia refers to the enormous burden for society caused by the dramatically increasing prevalence of severe cognitive impairment in aging societies. Several countries are beginning to prepare for these health and social challenges, and some have developed specific dementia plans. The main objectives of these strategies are to improve knowledge about dementia, provide better education and training for professionals, ensure that people with dementia are properly diagnosed, and develop a range of services for people with dementia and their carers (Howe, Reference Howe1997; Deutscher-Bundestag, 2002; Burns and Robert, Reference Burns and Robert2009). Although there is increased public awareness of dementia (Low and Anstey, Reference Low and Anstey2009), it still carries a huge stigma (Rimmer et al., Reference Rimmer2005; Burns and Iliffe, Reference Burns and Iliffe2009). Some dementia policy programs therefore prefer the label of “Alzheimer's disease” (Montgomery et al., Reference Montgomery2002), as do most patient and carer organizations. An interesting example of re-labeling is provided by a national project in Japan. The word for dementia “chihoushou” (
), which carries the deprecatory meaning of “stupidity” or “simple-mindedness,” was replaced by the more technical term “ninchishou” (
) which stands for “disease of knowledge and understanding”. This apparently simple change of words and characters has led to more positive ways of responding to the changes of brain aging.
Conclusion
The concept of dementia refers to a major cluster of psychopathological symptoms in organic psychiatry. With few exceptions it arises from chronic or progressive diseases which affect large parts or strategic areas of the brain. We argue that this theoretical construct continues to be valuable both for diagnosis and management, irrespective of the designation attached to it. It is useful for diagnosis because it directs clinicians to an underlying chronic, irreversible or progressive brain disease. The diagnostic role of the concept is not without limitations. First, the association of dementia with a particular group of underlying causes is imperfect, and potentially reversible etiologies must not be overlooked. Second, the concept of dementia is not helpful in the identification of irreversible or progressive brain diseases at a stage of minor symptoms. Such early diagnosis will increasingly become available in research settings through the development of neurobiological indicators of brain pathologies. Third, the concept is currently biased toward the memory-dominant subtype of AD and fits only poorly other subtypes such as frontotemporal degeneration or cerebrovascular disease. This limitation of the concept could be corrected in future editions of the psychiatric classification systems by emphasizing the psychopathological heterogeneity of the syndrome while retaining the core features of general intellectual decline and clear consciousness.
The concept of dementia also has an important role in patient management. It implies a complex pattern of impairments including cognition, behavior and functional ability, all of which are likely to worsen over time. This means that patients require intensive and long-term support, treatment and, possibly, supervision. The interpersonal concomitants of dementia indicate that in most cases it is not just one person who is affected by it but a social group. Dementia involves patients’ needs as well as benefits in terms of specific treatments and services. On the other hand, the approval of specific medications such as cholinesterase inhibitors for dementia in AD and Parkinson's disease precludes the use of these drugs in individuals who have these diseases but are still at a pre-dementia stage.
For these reasons we conclude that the medical concept of dementia is still useful but requires amendment. We feel that a change in terminology is timely. The word “dementia” is not an appropriate term for a syndrome which in current medical usage encompasses a broad spectrum of clinical severity including minor degrees of intellectual impairment. The label is particularly gloomy and distressing for patients who are still capable of managing their lives, and it causes reluctance in physicians when establishing and disclosing the diagnosis. A new nomenclature will also be needed to keep pace with advancements in science. Diagnosis and treatment will increasingly shift to stages of brain disease that are some distance from the final stages of severe intellectual deterioration and functional disability where the label of dementia might be considered appropriate (Derouesné, Reference Derouesné2003; Trachtenberg and Trojanowski, Reference Trachtenberg and Trojanowski2008). Novel wording should also reflect the qualitative and quantitative heterogeneity of the syndrome, avoiding an undue emphasis on its cognitive components (Chiu, Reference Chiu1999). A new name for the spectrum of cognitive and behavioral impairment with clear consciousness must, of course, preserve the benefits for patients and carers that are currently associated with dementia.
While much may be gained from a novel terminology, little will be lost. The term dementia has met with increased public awareness but it is still fraught with stigma. Campaigns and national programs that are using the term could probably be as effective if they applied alternative verbal designations, as can be learnt from organizations and campaigns which sail under the flag of Alzheimer's disease.
Conflict of interest declaration
Nicola T. Lautenschlager is a Deputy Editor of International Psychogeriatrics.
Description of authors’ roles
Both authors contributed to the preparation and writing of the paper.
Acknowledgment
The authors gratefully acknowledge the Japanese linguistic advice received from Friedrich A. Kurz.
