He adds, “Urine color does appear to be useful in children and young adults, but by the time we get to age 65 it is not working well. This may relate to the reduced ability of our kidneys to concentrate urine as well as they — and we — age.”

“Medications can also alter urine color and concentration, and are more common as we age,” he says. “The difficulty is knowing the point at which we need to stop trusting urine tests to indicate hydration status. We are not sure of this yet.”

Dr. Marc I. Leavey of Mercy Medical Center, Lutherville-Timonium, Maryland, told Reuters Health by email, “This is a fascinating study. In the elderly, particularly in the warmer months, dehydration can be a real problem.”

“They often do not drink adequate fluid, and many will forgo air conditioning believing that the cost is excessive or they remember when they were children and did not need such frivolous devices. The result is a dehydrated senior with attendant physical and mental changes,” he explains.

“Caregivers often use relative weight and urine color to watch for signs of dehydration, believing that weight loss could mean fluid loss, and concentrated, dark urine could also point to the same issue. The authors of this study (show) the lack of reliability of essentially all commonly used indicators other than serum osmolality,” he says.

Dr. Leavey concludes that those who work with the elderly and others at risk of dehydration need to use the more accurate measure of dehydration until less invasive techniques become available.

The authors reported no funding source or conflicts of interest.