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Does drinking more water protect against declining kidney function in patients with chronic kidney disease?
In this randomized clinical trial that included 631 adult patients with chronic kidney disease, the 1-year decline in estimated glomerular filtration rate did not significantly differ between patients who were coached to drink more water compared with patients who were coached to maintain their usual intake (−2.2 vs −1.9 mL/min per 1.73 m2).
Coaching to increase water intake did not significantly slow the decline in kidney function in patients with chronic kidney disease at 1-year follow-up.
In observational studies, increased water intake is associated with better kidney function.
To determine the effect of coaching to increase water intake on kidney function in adults with chronic kidney disease.
Design, Setting, and Participants
The CKD WIT (Chronic Kidney Disease Water Intake Trial) randomized clinical trial was conducted in 9 centers in Ontario, Canada, from 2013 until 2017 (last day of follow-up, May 25, 2017). Patients had stage 3 chronic kidney disease (estimated glomerular filtration rate [eGFR] 30-60 mL/min/1.73 m2 and microalbuminuria or macroalbuminuria) and a 24-hour urine volume of less than 3.0 L.
Patients in the hydration group (n = 316) were coached to drink more water, and those in the control group (n = 315) were coached to maintain usual intake.
Main Outcomes and Measures
The primary outcome was change in kidney function (eGFR from baseline to 12 months). Secondary outcomes included 1-year change in plasma copeptin concentration, creatinine clearance, 24-hour urine albumin, and patient-reported overall quality of health (0 [worst possible] to 10 [best possible]).
Of 631 randomized patients (mean age, 65.0 years; men, 63.4%; mean eGFR, 43 mL/min/1.73 m2; median urine albumin, 123 mg/d), 12 died (hydration group [n = 5]; control group [n = 7]). Among 590 survivors with 1-year follow-up measurements (95% of 619), the mean change in 24-hour urine volume was 0.6 L per day higher in the hydration group (95% CI, 0.5 to 0.7; P < .001). The mean change in eGFR was −2.2 mL/min/1.73 m2 in the hydration group and −1.9 mL/min/1.73 m2 in the control group (adjusted between-group difference, −0.3 mL/min/1.73 m2 [95% CI, −1.8 to 1.2; P = .74]). The mean between-group differences (hydration vs control) in secondary outcomes were as follows: plasma copeptin, −2.2 pmol/L (95% CI, −3.9 to −0.5; P = .01); creatinine clearance, 3.6 mL/min/1.73 m2 (95% CI, 0.8 to 6.4; P = .01); urine albumin, 7 mg per day (95% CI, −4 to 51; P = .11); and quality of health, 0.2 points (95% CI, −0.3 to 0.3; P = .22).
Conclusions and Relevance
Among adults with chronic kidney disease, coaching to increase water intake compared with coaching to maintain the same water intake did not significantly slow the decline in kidney function after 1 year. However, the study may have been underpowered to detect a clinically important difference.
clinicaltrials.gov Identifier: NCT01766687.
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Corresponding Author: William F. Clark, MD, Victoria Hospital, 800 Commissioner’s Road E, A2-343, London, ON, Canada N6A 5W9 (firstname.lastname@example.org).
Accepted for Publication: March 29, 2018.
Author Contributions: Drs Clark and Sontrop had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Clark, Sontrop, Huang, Gallo, Moist, House, Weir, Garg.
Acquisition, analysis, or interpretation of data: Clark, Sontrop, Huang, Gallo, House, Cuerden, Weir, Bagga, Brimble, Burke, Muirhead, Pandeya, Garg.
Drafting of the manuscript: Clark, Sontrop, Huang, Garg.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Sontrop, Cuerden, Garg.
Obtained funding: Clark, Sontrop.
Administrative, technical, or material support: Clark, Huang, Gallo, Moist, Weir, Bagga, Burke, Muirhead, Garg.
Supervision: Clark, Huang, Gallo, Moist, Weir, Brimble, Muirhead, Pandeya.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Clark reports receipt of an unrestricted grant, personal fees (scientific advisory board), and travel support from Danone Research. Dr Sontrop reports other (travel support) from Danone Research. Dr Huang reports receipt of a grant from Danone Research. Dr Moist reports other (travel support and serving as chair of the ISN/Danone Hydration for Kidney Health Research Initiative) from Danone Nutrica. No other disclosures were reported.
Funding/Support: This study was funded by Danone Research and the Program of Experimental Medicine, Western University, Canada. Thermo Fisher Scientific provided the instrumentation, assay reagent, and disposables for the analysis copeptin. Dr Garg was supported by the Dr Adam Linton Chair in Kidney Health Analytics, and a Clinician Salary Award from the Canadian Institutes of Health Research.
Role of Funder/Sponsor: Danone Research requested that this study include the measure of creatinine clearance as a secondary outcome; aside from this, the study sponsors had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Additional Contributions: Michael Walsh, MD, PhD (McMaster University), and Daniel G. Biche, MD (University of Montreal), served on the data and safety monitoring board for this trial. Ivan Tack, MD, PhD (Toulouse Hospital), provided useful insight on renal physiology. None of these individuals received compensation for their contribution. We also acknowledge the 631 patients without whom this investigation would not be possible.
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