Early onset dementia
Early onset dementia is dementia in which symptoms first appear before the age of 65. The term favored until about 2000 was presenile dementia; young onset dementia is also used.Early onset dementia may be caused by degenerative or vascular disease, or it may be due to other causes, such as alcohol-related dementia and other inflammatory or infectious processes. Early-onset Alzheimers disease, vascular dementia and frontotemporal lobar degeneration are the most common forms of early onset dementia, with Alzheimers accounting for between 30 and 40%. Early onset dementia may also occur, less frequently, in the Lewy body dementias (dementia with Lewy bodies and Parkinsons disease dementia), multiple sclerosis, Huntingtons disease and other conditions.

References
Further reading
Collins JD, Henley SM, Suárez-González A (July 2020). "A systematic review of the prevalence of depression, anxiety, and apathy in frontotemporal dementia, atypical and young-onset Alzheimers disease, and inherited dementia". Int Psychogeriatr (Review): 1–20. doi:10.1017/S1041610220001118. PMID 32684177. S2CID 220653830.
Ducharme S, Dols A, Laforce R,  et al. (June 2020). "Recommendations to distinguish behavioural variant frontotemporal dementia from psychiatric disorders". Brain (Review). 143 (6): 1632–1650. doi:10.1093/brain/awaa018. PMC 7849953. PMID 32129844.
Nwadiugwu M (September 2021). "Early-onset dementia: key issues using a relationship-centred care approach". Postgrad Med J (Review). 97 (1151): 598–604. doi:10.1136/postgradmedj-2020-138517. PMC 8408578. PMID 32883770.
Roman de Mettelinge T, Calders P, Cambier D (2021). "The Effects of Aerobic Exercise in Patients with Early-Onset Dementia: A Scoping Review". Dement Geriatr Cogn Disord (Review). 50 (1): 9–16. doi:10.1159/000516231. PMID 33957623. S2CID 233983643.