DEHYDRATION: SPECIAL DANGER FOR THE ELDERLY
As we grow older, we gradually lose our sense of thirst and can become dangerously dehydrated without realizing it. The New England Journal of Medicine (311,753) reports that elderly people tend not to drink enough to make up for the fluids lost by excessive sweating during infections or fever or following treatment with a diuretic (“water pill”).
In a study at Oxford, a group of men 67 to 75 years old was compared with another group aged 20 to 31. After 24 hours without fluids, the older men experienced surprisingly little thirst or discomfort, whereas the younger men were anxious to drink copious amounts of fluid. The older men were just as dehydrated as the younger ones but did not take as much of the fluid made freely available to everybody. Even though we do not know the cause of this difference in behavior, it is important to recognize it and to make up for it as we grow older by routinely drinking several glasses of water every day.
Like all other creatures, we are composed mainly of water. Soon after conception, the embryo is about 90 percent water but changes throughout gestation, so that just before birth the fetus is only about 80 percent water. By the time we reach maturity the percentage is 70 percent, and in our old age it falls below 60 percent, Geriatrics (42#6:53) reports. Since water is a good insulator, as we grow older we have trouble keeping warm during cold weather and staying cool when it is hot.
Making life still more difficult for senior citizens, old kidneys are less able than young ones to produce concentrated urine. Therefore, complications of dehydration in the elderly include kidney diseases (infections and stones) and excessive responses to medications that are eliminated from the body through the kidneys. Drugs affected by this include many hypertension drugs, heart medicines, and “water pills.”
Most seriously, what would be only a minor ailment in a young person could be the final illness for someone older who is dehydrated, Drug Therapy (17#1:56) reports. Elderly persons who become dehydrated have a much higher than expected mortality rate from infections because, when they do not drink enough to make up for their fluid losses (from sweating and vomiting, etc.), their blood becomes so much thicker that their kidneys cannot filter it well enough to get rid of body wastes. A vicious cycle occurs when consciousness becomes impaired by these wastes accumulating in the blood. The victim is then no longer able to drink extra fluid even when advised to do so. Administration of fluids intravenously becomes necessary.
To avoid these potentially very serious problems, older people must realize that thirst is no longer a reliable guide to their fluid needs, but often lags two to three days behind actual requirements. When healthy, a simple rule of thumb is to drink enough fluids to keep the urine a pale yellow rather than dark in color and to keep it coming in fair volume (at least four pints of urine daily). When you are ill or have fever, you should make it a point to drink more than usual, unless told otherwise.
A good way to make sure that you do not become dehydrated when taking exercise in a hot climate is to weigh yourself several times a day and to drink a pint of fluid for every pound that you have lost. Since prevention is better than cure, you should also drink one to two pints of fluid half an hour before taking part in any prolonged types of exercise, such as a few sets of tennis or 18 holes of golf.
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