The Importance of Hydration for People Living with Dementia

How the body regulates hydration

The human body regulates hydration through a balance of water intake and loss. When the body loses water (through sweating, breathing, or urination), the brain detects this using sensors in the blood and triggers thirst, prompting you to drink. At the same time, a hormone is released, signaling the kidneys to conserve water and produce less urine. Once you drink enough, the body adjusts, and hormone levels return to normal, allowing excess water to be removed. This delicate system keeps your body’s water levels stable, supporting essential functions like temperature control, digestion, and circulation.

Older People and hydration

Older people are more prone to dehydration owing to their reduced ability to regulate water and electrolytes, such as sodium / salt (1). The body typically uses the concentration of electrolytes in cells to trigger thirst (2), however in older people this can be too concentrated or not concentrated enough.

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7% of 65 year olds living at home and without acute illness had very low blood sodium concentrations (2)

34% of nursing home patients who developed acute illness requiring hospitalization had very high blood sodium concentrations (2)

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Dehydration and dementia

In people living with dementia, dehydration is exacerbated by the nature of their condition and symptoms are unique to each individual. However this can be categorised based on the known stages of dementia and associated disorders.

Dementia related disorder	Affect on hydration	Stage of dementia
Sense of smell and taste	Reduced desire to have tasty drinks. Reduced food intake accounting for 20-30% of total fluid intake (3)	Pre-clinical and early
Attention deficit	Disruption of routines that may include eating or drinking. Distraction away from drinking enough, or remembering to drink.	Mild to moderate
Impaired executive functions	Difficulty recognizing the need to drink, deciding when or how to get water, or remembering the steps involved (finding a glass, filling it, and drinking).	Mild to moderate
Impaired decision making ability	The ability to identify the importance of drinking regularly, or understanding the signs of dehydration (including darker urine or reduced volume, dry mouth, thirst, headaches).	Mild to moderate
Dyspraxia (coordination disorder)	Ability to hold a glass / cup and raise it to their mouth without spilling it.	Moderate to severe
Agnosia (recognise objects or their meaning)	Ability to identify items neccessary for drinking, such as cups, glasses, taps, water containers. Given the contribution of food for hydration (20-30%), it's also the ability to use utensils and prepare or source food.	Moderate to severe
Behavioural problems	Resisting offers of fluids.	Moderate to severe
Agitation / wandering	If the individual is consistently moving, this can create a bigger demand for fluid, owing to increased breathing and sweat rate.	Moderate to severe
Oropharyngeal dysphagia (swallowing disorder)	A disorder of the mouth and/or throat that makes it difficult moving food or fluid from the mouth to the stomach.	Moderate to severe
Refusal to eat	Reduced food intake accounting for 20-30% of total fluid intake (3)	Severe

Table adapted from Volkert et al (2024) and ESPEN guidelines on nutrition in dementia (4)

Dehydration and confusion

The relationship between dehydration and confusion isn't clear cut, and there are some mixed research results; in particular with individuals living with dementia.

In older adults in long-term residential care homes, dehydration was associated with level of cognitive impairment (or, it is possible that cognitive impairment was a risk factor for dehydration) (5).

Two hospital based studies found conflicting results between dehydration and dementia or confusion state. One found no difference (6), and one found that mental function was negatively affected by dehydration (7).

Dehydration and hospitalization

Dehydration can cause electrolyte imbalances, leading to confusion, dizziness, and an increased risk of falls or fainting, which may result in injuries. It can also trigger urinary tract infections (UTIs), kidney issues, and worsen pre-existing conditions like heart disease or diabetes.

Photo by Laura Margarita Cedeño Peralta on Unsplash

References

1. Schols, J.M.G.A., De Groot, C.P.G.M., Van Der Cammen, T.J.M. and Olde Rikkert, M.G.M., 2009. Preventing and treating dehydration in the elderly during periods of illness and warm weather. JNHA-The Journal of Nutrition, Health and Aging, 13, pp.150-157.

   
   

2. Popkin, B.M., D'Anci, K.E. and Rosenberg, I.H., 2010. Water, hydration, and health. Nutrition reviews, 68(8), pp.439-458.

   
   

3. Iversen, P.O. and Fogelholm, M., 2023. Fluid and water balance: a scoping review for the Nordic Nutrition Recommendations 2023. Food & Nutrition Research, 67.

   
   

4. Volkert, D., Beck, A.M., Faxén-Irving, G., Frühwald, T., Hooper, L., Keller, H., Porter, J., Rothenberg, E., Suominen, M., Wirth, R. and Chourdakis, M., 2024. ESPEN guideline on nutrition and hydration in dementia–Update 2024. Clinical Nutrition, 43(6), pp.1599-1626.

   
   

5. Hooper, L., 2016. Why, oh why, are so many older adults not drinking enough fluid?. Journal of the Academy of Nutrition and Dietetics, 116(5), pp.774-778.

   
   

6. McCrow, J., Morton, M., Travers, C., Harvey, K. and Eeles, E., 2016. Associations between dehydration, cognitive impairment, and frailty in older hospitalized patients: an exploratory study. Journal of gerontological nursing, 42(5), pp.19-27.

   
   

7. Seymour, D.G., Henschke, P.J., Cape, R.D.T. and Campbell, A.J., 1980. Acute confusional states and dementia in the elderly: the role of dehydration/volume depletion, physical illness and age. Age and ageing, 9(3), pp.137-146.