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Is Mild Cognitive Impairment a Valid Target of Therapy

Published online by Cambridge University Press:  02 December 2014

Kenneth Rockwood ,
Howard Chertkow  and
Howard H. Feldman
Kenneth Rockwood*
Affiliation:
The Department of Medicine (Geriatric Medicine & Neurology), Dalhousie University, Halifax, NS
Howard Chertkow
Affiliation:
Department of Medicine (Neurology), McGill University, Montreal, QC
Howard H. Feldman
Affiliation:
Department of Medicine (Neurology), University of British Columbia, Vancouver, BC, Canada
*
Centre for Health Care of the Elderly, 1421-5955 Veterans' Memorial Lane, Halifax, Nova Scotia, B3H 2E1, Canada.
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Abstract

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The status of Mild Cognitive Impairment (MCI) as a valid construct is controversial. The term encompasses people with heterogeneous clinical profiles, and invites sub-classifications that still require validation. Still, much evidence suggests that, properly selected, many people with MCI - especially Amnestic MCI - are at a high risk of dementia. This paper considers the validity of the construct of MCI as a high-risk state for progression and a target for treatment. We conclude that the status of MCI as an entity remains controversial. On the one hand, it can be argued that the careful section of cases at high risk of developing dementia means that it is a valid target, with the goal being the prevention of dementia. Advocates of this view see a linear progression that they are trying to arrest, but studies have yet to show that this can be done. On the other hand, it can be argued that the patients who progressed did not develop dementia: they actually had a very early form of it. By this view, people without the progressive form will be needlessly exposed to antidementia drugs, and the others should be treated anyway. Why some people progress and others do not is not clear, but the variable rates of progression - between clinic-based and population-based samples and between very similar clinical trials with slightly different inclusion criteria - suggests that MCI is a heterogeneous entity. The phenomenon of slowing or non-progression itself should be investigated, and such investigations likely should extend to people now classified as having mild dementia.

Résumé:

RÉSUMÉ:

Le statut du déficit cognitif léger (DCL) en tant que concept valide est controversé. Le terme désigne des individus qui ont des profils cliniques hétérogènes et il ouvre la voie à des sous-classifications qui n'ont pas été validées. Cependant il existe beaucoup de données indiquant que, s'ils sont choisis adéquatement, plusieurs individus ayant un DCL, spécialement le DCL amnésique, sont à haut risque de démence. Cet article examine la validité du concept du DCL comme un état à haut risque de progression et une cible de traitement. Nous concluons que le statut du DCL comme entité demeure controversé. D'une part, on peut considérer qu'une sélection précise des cas à haut risque de développer une démence indique qu'il s'agit d'une cible valide, le but étant la prévention de la démence. Ceux qui défendent cette position considèrent qu'il s'agit d'une progression linéaire qu'ils veulent tenter d'arrêter. Cependant les études n'ont pas démontré qu'il est possible de le faire jusqu'à maintenant. D'autre part, on peut considérer que les patients qui ont progressé n'ont pas développé une démence : ils avaient en fait une forme très précoce de démence. Si on adopte ce point de vue, les individus qui n'ont pas la forme progressive seront exposés inutilement aux médicaments anti-démence et les autres devraient être traités de toute façon. On ne sait pas pourquoi le déficit cognitif progresse chez certains individus et pas chez d'autres, mais le taux variable de progression - entre des échantillons recrutés en clinique et des échantillons recrutés dans la population, et entre des essais cliniques très similaires ayant des critères d'inclusion légèrement différents - suggère que le DCL est une entité hétérogène. Le phénomène de la progression lente ou de l'absence de progression devrait faire l'objet d'études et ces études devraient inclure des individus qu'on classifie actuellement comme ayant une démence légère.

Type
Original Articles
Information
Canadian Journal of Neurological Sciences , Volume 34 , Issue S1 , March 2007 , pp. S90 - S96
Copyright
Copyright © The Canadian Journal of Neurological 2007

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