Dementia

The answer first

Dementia is progressive decline in cognition across multiple domains, sufficient to interfere with independence, that is not delirium and not depression. It is not one disease but a syndrome with at least five underlying pathologies, each with a different course, a different drug, and a different trap. Alzheimer disease is the commonest, at 60 to 70 percent of cases.[1]

Five rules run the topic. First, it is a clinical diagnosis, anchored by the collateral history — no blood test or scan makes it; you prove a decline from a documented baseline across several domains, confirmed by a carer, having excluded delirium, depression, and the reversible mimics. Second, the subtype matters more than the label — it decides which drug helps (cholinesterase inhibitors help Alzheimer and Lewy body, not frontotemporal) and which drug kills (antipsychotics in Lewy body). Third, exclude the reversible causes before you settle — B12, TSH, depression, normal pressure hydrocephalus, subdural, and drug burden. Fourth, management is mostly non-pharmacological — cognitive enhancers give a modest symptomatic gain, not a cure. Fifth, antipsychotics are dangerous, and in Lewy body dementia they are absolutely contraindicated.[1]

The classic trap: when asked "best initial management of behavioural and psychological symptoms of dementia," the answer is almost always search for a precipitant (pain, infection, constipation, environment, drug), fix it, and use non-pharmacological strategies — not an antipsychotic. Risperidone is the only agent subsidised for this use, and only for severe aggression, time-limited to 12 weeks.[1]

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1. [1]Livingston G, Huntley J, Sommerlad A, et al. Dementia prevention, intervention, and care: 2020 report of the Lancet Commission Lancet, 2020.PMID 32738937
2. [2]Nasreddine ZS, Phillips NA, Bédirian V, et al. The Montreal Cognitive Assessment, MoCA: a brief screening tool for mild cognitive impairment J Am Geriatr Soc, 2005.PMID 15817019
3. [3]Petersen RC Clinical practice. Mild cognitive impairment N Engl J Med, 2011.PMID 21651394
4. [4]Birks J Cholinesterase inhibitors for Alzheimer's disease Cochrane Database Syst Rev, 2006.PMID 16437532
5. [5]McShane R, Westby MJ, Roberts E, et al. Memantine for dementia Cochrane Database Syst Rev, 2019.PMID 30891742
6. [6]Schneider LS, Dagerman KS, Insel P Risk of death with atypical antipsychotic drug treatment for dementia: meta-analysis of randomized placebo-controlled trials JAMA, 2005.PMID 16234500
7. [7]McKeith IG, Boeve BF, Dickson DW, et al. Diagnosis and management of dementia with Lewy bodies: Fourth consensus report of the DLB Consortium Neurology, 2017.PMID 28592453
8. [8]Rascovsky K, Hodges JR, Knopman D, et al. Sensitivity of revised diagnostic criteria for the behavioural variant of frontotemporal dementia Brain, 2011.PMID 21810890
9. [9]Hsieh S, Schubert S, Hoon C, et al. Validation of the Addenbrooke's Cognitive Examination III in frontotemporal dementia and Alzheimer's disease Dement Geriatr Cogn Disord, 2013.PMID 23949210
10. [10]Ngandu T, Lehtisalo J, Solomon A, et al. A 2 year multidomain intervention of diet, exercise, cognitive training, and vascular risk monitoring versus control to prevent cognitive decline in at-risk elderly people (FINGER): a randomised controlled trial Lancet, 2015.PMID 25771249
11. [11]Mitchell SL, Teno JM, Kiely DK, et al. The clinical course of advanced dementia N Engl J Med, 2009.PMID 19828530