Dementia And Hydration

What is dementia?

Dementia is a term used by health professionals to describe common symptoms like memory loss and confusion, but also problems with speech and understanding, that worsens over time. Dementia is not a specific disease; however, several diseases can cause dementia. Having memory loss alone does not mean you have dementia, but it can be an early sign.

The most well-known type of dementia is Alzheimer’s disease; however, there are more than 200 subtypes of dementia, like vascular dementia or Lewy body dementia. Each type of dementia stops a person’s brain cells (or neurons) in specific areas from working properly. This decline in brain function causes their ability to remember, think, and speak to be affected.

By 2025, it is estimated that over one million people in the UK will have a diagnosis of dementia.1 Dementia is typically seen in people over the age of 65, but it can affect people of all ages. It is important to note that dementia is not a natural part of ageing.2

Symptoms of dementia

The problems most described include issues with memory loss, speed of thinking, mental acuity, understanding, judgement, mood (managing behaviour or emotions), movement, doing daily activities, but also with language, like using words incorrectly or having trouble speaking. Aspects of your personality may change as well, and you may lose empathy or lose interest in relationships and socialising. Additionally, you may start to have hallucinations.2

As dementia progresses, it will become increasingly more difficult to maintain your independence as you will struggle to remember events and even things like when you have had your last meal or drink.

Can dehydration cause dementia?

Studies have shown that you only need to be 1% dehydrated to experience a 5% decrease in cognitive function. A 2% decrease in brain hydration can have short-term memory loss as a result. Staying dehydrated for prolonged periods of time will cause the brain cells to shrink in size and mass.3
In young people, specifically those assigned female at birth, these cognitive deficits were not permanent and were seen to be reversible by replenishing fluids.4 However, in the elderly, it was seen that the prolonged cellular stresses of dehydration could promote brain pathology and continue the decline in brain function. When older than 65 years, dehydrated individuals were placed at a higher risk for dementia.5

Severe dehydration and dementia show similar symptoms

Severe dehydration will show similar symptoms to dementia. They include memory issues, mental confusion, cognitive decline, changes in behaviour, weakness, fatigue, agitation, and dizziness. Also important to note is that being dehydrated can increase the risk of a urinary infection, which can also cause an acute phase of confusion in the elderly.3-6

Dehydration is common in people with dementia

Parts of the brain that act on the feeling of thirst/recognize thirst are commonly affected by dementia. With age, the brain also becomes less sensitive to sensing thirst, making it a less reliable indicator of hydration status.7 Additionally, the person with dementia may not remember being thirsty or how to get themselves a glass or some water. Maybe their verbal communication has declined so far that they cannot express their thirst, or they do not understand why they need to drink. They could be on medication increasing their output in urine or perspiration, so they will need to drink more than usual. They could suffer from a fear of incontinence, so they will restrict their fluid intake, causing them to be dehydrated.5,8


It is important to stay well hydrated. Studies have shown that 1% dehydration can cause a 5% decrease in cognitive function. To keep a healthy adult hydrated, they need to be drinking about 6-8 glasses of water daily. When a person has dementia, it can become a challenge to make sure they drink enough water in a day. It is important for them to have reminders to drink, in the form of a helpful water bottle with a straw they can carry with them or little alarms or notices that will nudge them to drink water. It is also an idea to give them foods with higher water content, like cucumber or watermelon, and provide easy access. People who become dehydrated show a decline in brain function, which can be reversed if spotted early; however, if left for a long time, it can become permanent as the brain cells shrink in size and mass.


  1. Dementia UK [Internet]. What is dementia?; [cited 2022 Sep 26]. Available from:
  2. About dementia. NHS.UK [Internet]. 2017 [cited 2022 Sep 26]. Available from:
  3. Wittbrodt MT, Millard-Stafford M. Dehydration Impairs Cognitive Performance: A Meta-analysis. Medicine & Science in Sports & Exercise [Internet]. 2018 [cited 2022 Sep 26]; 50(11):2360–8. Available from:
  4. Stachenfeld NS, Leone CA, Mitchell ES, Freese E, Harkness L. Water intake reverses dehydration associated impaired executive function in healthy young women. Physiol Behav. 2018; 185:103–11.
  5. Lauriola M, Mangiacotti A, D’Onofrio G, Cascavilla L, Paris F, Paroni G, et al. Neurocognitive Disorders and Dehydration in Older Patients: Clinical Experience Supports the Hydromolecular Hypothesis of Dementia. Nutrients [Internet]. 2018 [cited 2022 Sep 26]; 10(5):562. Available from:
  6. Griebling TL. Re: The Scientific Evidence for a Potential Link between Confusion and Urinary Tract Infection in the Elderly is Still Confusing-A Systematic Literature Review. J Urol. 2020; 203(6):1042.
  7. Sfera A, Cummings M, Osorio C. Dehydration and cognition in geriatrics: a hydromolecular hypothesis. Front Mol Biosci [Internet]. 2016 May 12 [cited 2022 Nov 5];3:18. Available from:
  8. Masento NA, Golightly M, Field DT, Butler LT, Reekum CM van. Effects of hydration status on cognitive performance and mood. Br J Nutr. 2014; 111(10):1841–52.

IIona Kosten

Master of Science - (MS), Immunology and Infectious diseases, Vrije Universiteit Amsterdam (VU Amsterdam), Netherlands

Ilona has a BSc and MSc in Biomedical Sciences and a PhD in Immunology with a sweet spot for “all things allergy”.
She’s published a number of articles in peer reviewed journals ranging from skin and mucosa tissue engineering, immunoassays, DCs, LCs and T cells." presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
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