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Water balance, thirst and ageing

Older people are more susceptible to dehydration because of physiological changes due to ageing which affect water metabolism and fluid balance. These changes include alterations in hormone levels, including antidiuretic hormone, atrial natriuretic peptide, and aldosterone, and a decline in kidney function including decreased glomerular filtration rate, decreased urinary concentrating ability and limitations in the excretion of sodium and potassium.(1) In particular, the decrease in urinary concentrating ability means that older people are more likely to lose water which, in younger adults, would be retained by the body to counteract dehydration.(1,2) Renal diluting ability can also decline with age, and so older people may be less able to excrete a large amount of water which was in excess of the body’s requirements.(3)

Older people also experience an age-related decrease in total body water, which declines from 60 per cent of body mass in a younger adult male, for example, to 50 per cent by the age of 80 years. In spite of these physiological changes, body fluid balance can usually be maintained under normal circumstances. Problems can occur, however, when the older person experiences fluid deprivation, either through cognitive impairment, changes in functional ability or medication such as diuretics and hypnotics (which increase water loss); suffers an illness; or is stressed as a result of other factors. Thus older people are prone to dehydration due either to reduced water intake or a greater water loss.(4,5)

Thirst and consequent fluid intake are the body’s natural defence mechanism against dehydration. However many studies have found that the thirst response is impaired in older people.(6) For example, they show a decreased thirst sensation and reduced fluid intake in response to: fluid deprivation; a warm hyperosmotic stimulus; hypovolaemia; exercise in a warm environment;(8) and stimulation of the baroreceptors which monitor total body water.(7) It should be noted, however, that there are a few studies in which no age difference in thirst response was demonstrated.(8,9,6).

Some conditions associated with ageing can also adversely affect the thirst response. Thirst can be severely impaired in patients with a prior history of stroke, but who do not have cognitive impairment or evidence of hypothalamic or pituitary dysfunction.(10) Loss of the protective "thirst" response has also been shown in patients with Alzheimer's disease, making them at particular risk of dehydration.(11)

Risk factors for dehydration in older people

 •  Age >85 years
 •  Thirst reduction
 •  Problems with access to drink
 •  Communication problems
 •  Cognitive disorders
 •  Swallowing difficulty
 •  Reduced appetite
 •  Medications (eg diuretics, laxatives, sedatives)
 •  Acute pathology (eg fever, vomiting, diarrhoea)
 •  Lack of attention from caregivers.(12)

Detecting dehydration in older people

In older people the signs of dehydration may be absent or misinterpreted because of the effects of normal ageing. Dehydration may not become apparent until the person develops another concomitant illness, such as urinary tract infection.(13) In addition, since the signs and symptoms of dehydration in older people are more subtle than in younger patients, they may not become apparent until they are more pronounced.(14) One study found that chronic dehydration was present in 48 per cent of older adults who visited an emergency department in June 2000. In spite of this, only 26 per cent had assessment for signs of dehydration documented by doctors, indicating that dehydration may often be unrecognised.(15)

The clinical signs of dehydration can be misleading. Severe postural dizziness or a postural pulse increment of 30 beats per minute or more are useful physical findings which can indicate dehydration.(16) The main clinical signs of dehydration in older people are listed below:

 •  Altered thirst
 •  Neuropsychic symptoms (especially confusion)
 •  Arterial ischaemia or phlebitis
 •  Mucosal dryness (eg dry mouth)
 •  Fever (occasionally)
 •  Cardiovascular signs: arterial hypotension (especially orthostatic hypotension), tachycardia
 •  Weight loss
 •  Sunken eyes
 •  Concentrated urine
 •  Lasting skinfold(13)

Given the paucity of sensitive clinical signs, laboratory evaluation is the preferred tool in the hospital setting.(17) There are many ways of measuring hydration status using laboratory techniques, such as bioelectrical impedance analysis, urine, blood and saliva parameters. (see also Dehydration: Ways to measure dehydration) For older people, observation of the rate and degree of filling of small veins in the foot* has been shown to be a good indicator of hydration status. This may be a quick and easy method to monitor levels of hydration, allowing caregivers to identify those needing increased fluid intake at an early stage.(14)

*Using this measure a dorsal foot vein is occluded by finger pressure at a distal point and emptied by stroking proximally. The pressure is then released
and rate and degree of return of blood is observed and rated.(14)

Levels of dehydration in older people

Dehydration may be present in as many as 25 per cent of older people, and higher rates have been found in care home residents who have been referred to hospital with fever.(17) A survey of water provision in UK care homes for the elderly in 2003(18) found that most residents only consumed 2-4 glasses of water/fluid per day (480-960ml). Although 90 per cent of responding care homes actively encouraged residents to drink water, residents were often reluctant, preferring other drinks such as tea or coffee, which can have diuretic effects. Water intake was rarely included in care plans for individual residents.

In 2006 the English Community Care Association found that awareness of the importance of hydration in care homes had increased, but there was a need for clearer understanding of hydration policies. Thirty two per cent of respondents said that water was available throughout the care home in all communal rooms, with 31 per cent placing fresh water jugs throughout the building. However, 24 per cent only provided water on request and in 15.5 per cent of cases, water was only available at mealtimes.(19)

One of the main dehydration risk factors for people with poor mobility or cognitive impairment is not having access to water. In spite of this, one study of people over 75 years of age found that 77 per cent preferred to buy and transport bottled water, even though they had some difficulty in carrying heavy items. This potentially limited their water intake when tap water is safe and could have been used instead.(13)

Water requirements in older people

Older people have the very similar water requirements to those of younger adults. Earlier estimates recommended that total water intake (including water contained in food) should be approximately 1ml per kcal of energy expenditure per day.(20) More recent guidance(21) has recommended that for adults aged 51 and above, the total water intake should be 3.7 litres per day for men and 2.7 litres per day for women. This estimate includes water contained in food and the amount to be obtained from beverages is estimated to be approximately 3 litres for men and 2.2 litres for women. These figures are based on an individual who undertakes 60 minutes of moderate physical activity throughout the day and consumes a diet containing about 2200 kcal.

Other estimates suggest that the daily water requirement for older dependent persons can be calculated more accurately using the following formula: 100ml fluid per kilogram for the first 10kg actual body weight, 50ml fluid per kilogram for the next 10kg actual body weight, and 15ml fluid per kilogram for the remaining kilograms of actual body weight.(22)

Values for minimum water requirements for inactive adults in a temperate climate range from 1 to 3.1 litres per day to replace losses from respiration, urine, faeces and sweating.(22) One conservative estimate for older adults is that daily intake of fluids should not be less than 1.6 litres per day in order to ensure adequate hydration.(23) The “Apports Nutritionnels Conseilles” (the nutritional reference values for the French population) recommends at least 1.5 litres per day, which should be increased when the outside temperature rises, when the inside temperature is overheated, or when the patient has a fever. In the case of a fever, 500ml more liquid per degree of fever above 38oC is recommended.(13)

The National minimum care standards - Care homes for older people(24) recommends that “Hot and cold drinks and snacks are available at all times and offered regularly.” Food, in the regulations, includes drink and the expected outcome of Care Standard 15 is that “service users receive a wholesome appealing balanced diet in pleasing surroundings at times convenient to them.” The National Minimum Care Standards are currently under review. Guidance on intrepreting the care standards in relation to drinking water can be found in the Caroline Walker Trust second edition of Eating Well for Older People.(25)

Adverse effects of dehydration in older people

There are a number of important adverse effects of dehydration in older people. These range from bedsores (see Pressure Ulcers),(26) constipation and faecal impaction (see Constipation), to cognitive impairment (see Mental Performance), functional decline and death.(7)

The risk of falls increases with age and in older people they can result in injury and death, often as a result of fractures. Dehydration is one of the risk factors for falls in older people. Even mild chronic hyponatraemia, which is generally considered as asymptomatic, can induce a high incidence of falls as a result of unsteadiness and other gait impairments as well as a deterioration in mental state,(27) which increases the risk of falls resulting from dizziness and fainting.(28,29) A degree of malnutrition and hypohydration is common in patients with hip fractrues. One study found that during their hospital stay, the fluid and energy intake of otherwise healthy hip fracture patients was considerably lower than needed.(30) Dietary interventions aimed at reducing injuries from falls tend to focus on vitamin D and calcium supplementation since this can be effective in reducing the number of fractures in older people who are at risk of falling.(31,32). However, the maintenance of adequate levels of hydration in older people is also important in preventing falls, particularly if it was incorporated as part of a multifactoral falls prevention strategy.(29) In hard water areas, tap water can also provide a significant proportion of dietary calcium, which is essential for good bone mineral density and the prevention of osteoporosis and fractures.(33)

Dehydration is an important cause of hospitalisation in older people. It has been shown to increase by two-fold the hospital mortality in patients admitted with stroke. It also increases the length of hospital stay in patients with community-acquired pneumonia.(17) In 1999, the economic cost of unnecessary hospitalizations associated with dehydration in US older patients was estimated at 1.14 billion dollars. The average length of hospital stay was 4.6 days.(34)

Last updated: January 2007

1. O'Neill PA, McLean KA. Water homeostasis and ageing. Med Lab Sci. 1992;49:291-8
2. Rolls BJ, Phillips PA. Aging and disturbances of thirst and fluid balance. Nutr Rev 1990;48:137-44
3. Crowe MJ, Forsling ML, Rolls BJ, Phillips PA, Ledingham JG, Smith RF. Altered water excretion in healthy elderly men. Age Ageing 1987;16:285-93
4. Naitoh M, Burrell LM. Thirst in elderly subjects. J Nutr Health Aging 1998;2:172-7
5. Stout NR, Kenny RA, Baylis PH. A review of water balance in ageing in health and disease. Gerontology 1999;45:61-66
6. Kleiner SM. Water: An essential but overlooked nutrient. J Am Diet Assoc 1999:99:201-7
7. Kenney WL, Chiu P. Influence of age on thirst and fluid intake. Med Sci Sport Exer 2001;33:1524-32
8. Davies I, O'Neill PA, McLean KA, Catania J, Bennett D. Age-associated alterations in thirst and arginine vasopressin in response to water or sodium load. Age Ageing 1995;24:151-9
9. Stachenfeld NS, Mack GW, Takamata A, DiPietro L, Nadel ER. Thirst and fluid regulatory responses to hypertonicity in older adults. Am J Physiol 1996;271:R757-R765
10. Miller PD, Krebs RA, Neal BJ, McIntyre DO. Hypodipsia in geriatric patients. Am J Med 1982;73:354-6
11. Albert SG, Nakra BR, Grossberg GT, Carminal Er. Drinking behaviour and vasopressin responses to hyperosmolarity in Alzheimer's disease. Int Psychogeriatrics 1994;6:79-86
12. Ferry M. Strategies for ensuring good hydration in the elderly. Nutr Rev 2005;63:S22-S29
13. Rosher RB and Robinson SB. Use of foot veins to monitor hydration in the elderly. J Am Geriatr Soc 2004;52:322-4
14. Archibald C. Promoting hydration in patients with dementia in healthcare settings. Nursing standard 2006;20:49-52
15. Bennett JA, Thomas V and Riegel B. Unrecognized chronic dehydration in older adults: examining prevalence rate and risk factors. J Gerontol Nurs 2004;30:22-8
16. Thomas DR, Tariq SH, Makhdomm S, Haddad R, Moinuddin A. Physician misdiagnosis of dehydration in older adults. J Am Med Dir Assoc 2004;5:S31-34
17. Ferry M, Dardaine V, Constans T. Subcutaneous infusion or hypodermoclysis: a practical approach. J Am Geriatr Soc 1999;47:93-95
18. Water Provision in Care Homes For the Elderly. A survey by the Royal Society for the Promotion of Health, in cooperation with the Water for Health Alliance. October 2003.
19. English Community Care Association, Well watered residents and staff? August 2006
20. Food and Nutrition Board. Recommended Dietary Allowances. 10th ed. Washington, DC: National Academy Press;1989
21. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride and Sulfate (2004) Institute of Medicine of the National Academies. Washington DC: The National Academies Press
22. Chidester JC, Spangler AA. Fluid intake in the institutionalised elderly. J Am Diet Assoc. 1997;97:23-28
23. Hodgkinson B, Evans D, and Wood J. Maintaining oral hydration in older adults: a systematic review. Int J Nurs Pract. 2003;9:S19-28
24. Department of Health. Care Homes for Older People. National Minimum Standards London: TSO 2003
25. The Caroline Walker Trust. Eating well for older people. 2004 (For extract see: Water UK, Review of existing care guidance)
26. National Institute for Clinical Excellence. Pressure ulcer risk assessment and prevention. Inherited Clinical Guideline B. London: NICE April 2001
27. Renneboog B, Musch W, Vandemergel X, Manto MU, Decaux G. Mild chronic hyponatremia is associated with falls, unsteadiness, and attention deficits. Am J Med 2006;119:e1-8
28. American Geriatrics Society, British Geriatrics Society and American Academy of Orthopaedic Surgeons Panel on Falls Prevention. Guidelines for the prevention of falls in older persons. J Am Geriatr Soc 2001;49:664-672
29. Sankar NS, Donaldson D. Lessons to be learned: a case study approach diuretic therapy and a lazative causing electrolyte and water imbalance, loss of attention, a fall and subsequent fractures of the tibia and fibula in an elderly lady. J Roy Soc Health 1998;118:237-40
30. Eneroth M, Olsson UB, Thorngren KG. Insufficient fluid and energy intake in hospitalised patients with hip fracture. A prospective randomised study of 80 patients. Clin Nutr. 2005;24:297-303
31. Chapuy MC, Arlot ME, Duboeuf F, Brun J, Crouzet B, Arnaud S, Delmas PD, Meunier PJ. Vitamin D3 and calcium to prevent hip fractures in elderly women. New Engl J Med 1992;327:1637-42
32. Gillespie WJ, Henry DA, O'Connell DL, Robertson J. Vitamin D, vitamin D analogues and calcium in prevention of fractures in involutional and post-menopausal osteoporosis. Cochrane Database of Systematic Reviews 1996; issue 3
33. Expert Group on Vitamins and Minerals. Review of calcium. Food Standards Agency. EVM/01/12.REVISEDMAR2002.
34. Xiao H, Barber J, Campbell ES. Economic burden of dehydration among hospitalized elderly patients. Am J Health Syst Pharm. 2004;61:2534-40