Effect of Coaching to Increase Water Intake on Kidney Function Decline in Adults With Chronic Kidney Disease: The CKD WIT Randomized Clinical Trial

Abstract

Importance: In observational studies, increased water intake is associated with better kidney function.

Objective: 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.

Interventions: 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]).

Results: 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.

Trial registration: clinicaltrials.gov Identifier: NCT01766687.

Conflict of interest statement

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.

Figures

Figure.. Flow of Patients Through the Chronic Kidney Disease Water Intake Trial

aPrescreened by a research assistant for eligibility. bOther reasons: no urine protein, enrolled in another study, pregnant or breastfeeding, kidney stones in the past 5 years, less than 2 years of life expectancy, and gastrointestinal issues (eg, inflammatory bowel disease or Crohn disease). cOther reasons: too busy, did not want to undergo blood tests, did not want to undergo 24-hour urine collections, cancer diagnosis, physician advised not to participate. dOther reasons: medication contraindications or chemotherapy. eMedian time to death was 5.1 months (interquartile range, 3.1-7.3). fMedian time to death was 7.2 months (interquartile range, 2.0-10.2). eGFR indicates estimated glomerular filtration rate.