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NEW ORLEANS -- Drinking more water did not slow the decline in estimated glomerular filtration rate (eGFR) over 1 year in patients with chronic kidney disease (CKD), researchers said here.

The average 1-year decline in eGFR was 2.2 ml/min/1.73m² in the hydration group compared with 1.9 ml/min/1.73m² in the control group, with similar results seen in per protocol and sensitivity analyses, reported William F. Clark, MD, of Western University and London Health Sciences Centre in Canada, at ASN Kidney Week 2017.

Clark explained that the copious amount of literature on the benefits of drinking water inspired his group to study the effect of hydration on patients with CKD. However, the primary outcome of a reduction in eGFR was not met so he can't present it as a positive study, he told 番茄社区.

Kelly Hyndman, PhD, of University of Alabama at Birmingham, who was not involved with the study, commented on the findings, saying "hydration status in these patients, if you modify it, it causes no harms but provides no benefits."

One potential explanation for the the absence of an effect may be that a 1-year intervention is too short to produce a measurable effect on eGFR, Clark noted. He also suggested a need for greater hydration, as well as the idea that prior observational studies were confounded and that increased water intake does not protect against decline eGFR.

Clark 's group examined 631 patients with stage 3 CKD and a 24-hour urine volume that was less than 3 L from nine centers in Ontario, Canada. The average age of patients was 65, half were male, and 88% had hypertension.

Patients randomized to the hydration group (n=316) were coached to increase their oral water intake by 1-1.5 L/day, over and above usual consumed beverages, while those in the control group (n=315) maintained usual fluid intake.

All patients had monthly coaching sessions in which they completed a standardized survey with reference to quantity of water ingested relative to target intake. Nearly all (95%) patients provided 1-year eGFR measures.

The researchers found that the hydration group had lower plasma copeptin concentrations (between-group difference of -2.3 pmol/L, P<0.01) and higher creatinine clearance (between-group difference of 3.6 ml/min/1.73m², P<0.05) compared with placebo. Urine albumin and quality of life were similar between groups.

"Had creatinine clearance been a primary endpoint they would have shown that GFR was improved in CKD," Hyndman told 番茄社区. She commented that an interesting future study would be to investigate whether the benefit remained when using inulin clearance or if it relates more to creatinine metabolism.

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