Urine tests that can signal dehydration in young adults or children may not be so accurate in the over-65 group. The possible reasons are numerous — ranging from impaired kidney function to medications that affect urine color.
Dehydration can be a serious condition with symptoms ranging from slight dizziness to a propensity for heat stroke. And it can be more of a problem in the geriatric set because of blunted thirst sensations, impaired kidney function, neglecting eating or drinking regularly, medications, or medical conditions such as diabetes. There are several indications that a person is dehydrated, including less skin turgidity (plumpness), dry skin, thirst, dry sticky mouth, sleepiness or tiredness. A dehydrated person will also have a higher concentration of various minerals and proteins in their blood. Thus a person's blood may be sampled to determine their hydration status. And simplest of all is urine tests. First volume — a dehydrated person will not produce as much urine as when they were properly hydrated; it will be more concentrated (higher specific gravity) and can be darker than usual. These characteristics can be determined by a simple dip stick test, as in the picture above.
But not all these signs are accurate in older persons, according to research carried out at East Anglia University in Britain. Dr. Lee Hooper from UEA's Norwich Medical School was lead author on a study of 383 men and women aged over 65 living in residential care, nursing homes, or in their own homes in Norfolk and Suffolk. The investigators sampled the participants' blood to determine their hydration status, and also ran standard tests on urine samples to see how the two measures agreed.
They did not agree in all of the test cases. Sometimes the urine tests indicated a person was dehydrated when they were not. And of more concern, sometimes the urine test didn't catch that a person was dehydrated when, according to the more accurate blood tests, they actually were.
Dr. Hooper explained "Urinary tests rely on normal kidney function. While urine tests do seem to be able to indicate hydration status in children and younger adults, ageing is associated with impaired kidney function. As we get older we cannot concentrate our urine as well as younger people - so urine tests are not useful in older adults for indicating hydration."
In addition, she pointed out that some common medications such as warfarin (coumadin), often prescribed to older patients to prevent blood clots, can darken the urine — without there being real dehydration.
This is no reason, of course, to stop taking prescribed medications. Rather, it's important to be aware of such issues when a diagnosis is reliant upon urine tests.