Assessment of dementia

Dementia is a syndrome characterised by an appreciable deterioration in cognition resulting in behavioural problems and impairment in the activities of daily living. Decline in cognition is extensive, often affecting multiple domains of intellectual functioning.[1]American Psychiatric Association. Diagnostic and statistical manual of mental disorders, 5th ed., (DSM-5). Washington, DC: American Psychiatric Publishing; 2013.[2]Cummings JL, Benson DF. Dementia: a clinical approach. 2nd ed. Boston: Butterworth-Heinemann; 1992.

The prevalence of dementia is approximately 1% at the age of 60 years, and doubles every 5 years, to reach 30% to 50% by the age of 85 years.

The majority of cases of dementia have degenerative and vascular causes.[3]Thal LJ, Grundman M, Klauber MR. Dementia: characteristics of a referral population and factors associated with progression. Neurology. 1988 Jul;38(7):1083-90. http://www.ncbi.nlm.nih.gov/pubmed/3386827?tool=bestpractice.com [4]Corey-Bloom J, Thal LJ, Galasko D, et al. Diagnosis and evaluation of dementia. Neurology. 1995 Feb;45(2):211-8. http://www.ncbi.nlm.nih.gov/pubmed/7854514?tool=bestpractice.com [5]Roman GC, Tatemichi TK, Erkinjuntti T, et al. Vascular dementia: diagnostic criteria for research studies; report of the NINDS-AIREN International Workshop. Neurology. 1993 Feb;43(2):250-60. http://www.ncbi.nlm.nih.gov/pubmed/8094895?tool=bestpractice.com Other causes include infections, inflammatory diseases, neoplasm, toxic insults, metabolic disorders, and trauma.

An estimated 10% to 20% of dementias are caused by potentially reversible conditions; therefore, ruling out these conditions is of the utmost importance when considering a diagnosis of dementia.[6]Clarfield AM. The reversible dementias: do they reverse? Ann Intern Med. 1988 Sep 15;109(6):476-86. http://www.ncbi.nlm.nih.gov/pubmed/3046450?tool=bestpractice.com

A number of conditions can present in a similar way to dementia syndrome and need to be considered during the evaluation. These include delirium, depression, amnestic syndromes, aphasia, and normal ageing.