Several studies have demonstrated that elderly persons have lower total water intakes than younger adults, and that women are particularly at risk of too low an intake. In 2009, the European Food Safety Authority (EFSA) included water as a macronutrient in its dietary reference values for the first time. Recommended intake volumes in the elderly are the same as for younger adults (2.0 L/day for females and 2.5 L/day for males) as despite lower energy consumption, the water requirement of this group is increased due to a reduction in renal concentrating capacity. Thirst quenching
According to preliminary research, quenching of thirst – the homeostatic mechanism to stop drinking – occurs via two neural phases: a "preabsorptive" phase which signals quenched thirst many minutes before fluid is absorbed from the stomach and distributed to the body via the circulation, and a "postabsorptive" phase which is regulated by brain structures sensing  to terminate fluid ingestion. The preabsorptive phase relies on sensory inputs in the mouth, pharynx, esophagus, and upper gastrointestinal tract to anticipate the amount of fluid needed, providing rapid signals to the brain to terminate drinking when the assessed amount has been consumed.
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.