Dyke et al., 1997). Despite equivalent increases in plasma volume, the older group consumed significantly less water and had greater increases in serum osmolality than the younger group.

Thirst may also be severely impaired in patients with a prior history of stroke who do not have cognitive impairment or evidence of hypothalamic or pituitary dysfunction (Miller et al., 1982). The complication of age-related decreases in thirst by systemic illnesses and dementia in many frail elderly patients clearly place them at risk for the development of severe water deficiency.

Summary. While there are differences in renal physiology that occur with aging, Appendix Table G-1 (which provides serum osmolality values by percentile of water intake) indicates that hydration status continues to be normal over a wide range of intakes for elderly individuals as well as younger individuals. The AI for total water (drinking water, beverages, and foods) for the elderly is set based on median total water intake of young adults (Appendix Table D-1), rather than the older age group, in order to ensure that total water intake is not limited in the face of a potential declining ability to consume adequate amounts in response to thirst.