Age-related changes in hydration.

Abstract

Normal aging is often described as a continuous process characterized by a decrease in lean body mass, an increase in fat, and a decrease in total body water. However, it has been pointed out that many older people, especially those aged 75 years and over, may feel healthy in spite of a chronic illness [1]. Thus, both nutrition and hydration may be altered by chronic diseases, infection, as well as by changes in functional status, mobility disorders, confusion, impaired sensory perception, medication effects and difficulties in drinking, swallowing and eating because of the absence of teeth or ill-fitting dentures. For water balance, two factors place the elderly at risk for dehydration: a decreased fluid intake and an increased fluid loss. In the human, the normal pattern of drinking is intermittent while water is continuously lost by various routes so that dehydration occurs. Dehydration is the most common cause of fluid and electrolyte imbalance and is frequently reported in residents, hospitalized and community-dwelling elderly people. It has been stated that one of the greatest threats to the survival of any terrestrial animal, including man, is that of dehydration [2]. In this chapter we review the factors which may disturb fluid balance and predispose elderly to dehydration, the mechanisms involved and the changes in body water compartments. The possible health consequences of dehydration and the new recommendations of fluid intake in elderly populations are also discussed.