Assessment of dementia

Dementia is a syndrome characterised by deterioration in cognition, resulting in impairment in the activities of daily living. Cognitive decline often affects multiple domains.[1]American Psychiatric Association. Diagnostic and statistical manual of mental disorders, 5th ed., (DSM-5). Washington, DC: American Psychiatric Publishing; 2013.

The incidence of dementia doubles with every 6.3 year increase in age, from 3.9 per 1000 person-years at age 60-64, to 104.8 per 1000 person-years at age 90 and over.[2]Prince M, Wimo A, Guerchet M, et al. Alzheimer's Disease International. World Alzheimer Report 2015. Aug 2015 [internet publication]. https://www.alzint.org/u/WorldAlzheimerReport2015.pdf

The global number of individuals who lived with dementia increased from 20.2 million in 1990, to 43.8 million in 2016, and dementia was the fifth leading cause of death globally, accounting for 2.4 million deaths.[3]GBD 2016 Dementia Collaborators. Global, regional, and national burden of Alzheimer's disease and other dementias, 1990-2016: a systematic analysis for the Global Burden of Disease Study 2016. Lancet Neurol. 2019 Jan;18(1):88-106. https://www.doi.org/10.1016/S1474-4422(18)30403-4 http://www.ncbi.nlm.nih.gov/pubmed/30497964?tool=bestpractice.com It is thought that the number of people living with dementia will almost double every 20 years, reaching 75 million in 2030 and 131.5 million in 2050, with this increase predominantly affecting developing countries.[4]Alzheimer's Disease International. Dementia statistics. 2020 [internet publication]. https://www.alzint.org/about/dementia-facts-figures/dementia-statistics

The majority of cases of dementia have degenerative and vascular causes.[5]Goodman RA, Lochner KA, Thambisetty M, et al. Prevalence of dementia subtypes in United States Medicare fee-for-service beneficiaries, 2011-2013. Alzheimers Dement. 2017 Jan;13(1):28-37. https://www.doi.org/10.1016/j.jalz.2016.04.002 http://www.ncbi.nlm.nih.gov/pubmed/27172148?tool=bestpractice.com Other causes include infections, inflammatory diseases, neoplasm, toxic insults, metabolic disorders, and trauma.

An estimated 11% to 14% 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 [7]Clarfield AM. The decreasing prevalence of reversible dementias: an updated meta-analysis. Arch Intern Med. 2003 Oct 13;163(18):2219-29. https://www.doi.org/10.1001/archinte.163.18.2219 http://www.ncbi.nlm.nih.gov/pubmed/14557220?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.