Body water in the elderly--a review.

Body composition including the amount, the proportion of body weight, and the distribution of body water are of profound interest to both gerontology and geriatric medicine. In this article, methods of estimating body water, the changes with age and in disease, and clinical implications are reviewed. There are many methods to determine body water, the methods having different properties regarding e.g. feasibility and validity. Validation should for the methods used be performed in the population and age group under study. Body water decreases with age, and increases or decreases of body water are common in diseases common in old age. This has obvious clinical implications regarding e.g. geriatric pharmacotherapy, and water and electrolyte therapy. The need for methods to estimate body water and for avoiding both underhydration and overhydration is obvious both in gerontological and geriatric research and in clinical geriatric medicine.