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Coaching adults with chronic kidney disease (CKD) to increase their daily water intake did not noticeably prevent the decline of kidney function, according to the findings of a recent study published in JAMA.
Conditions of the Study
Researchers conducted the CKD WIT (Chronic Kidney Disease Water Intake Trial) in nine clinics across Ontario, Canada to determine whether coaching patients with chronic kidney disease to drink more water could slow kidney function decline.
Among 631 patients with stage 3 chronic kidney disease and a 24-hour urine volume lower than 3.0 L, 316 were placed in a hydration group and coached on the phone once a month to increase the amount of water they drink for one year. This increase varied between 1.0 and 1.5 L per day based on each patient’s sex and weight. The other 315 patients were placed in a control group and coached to drink the same amount of water as usual or decrease their intake by 0.25 to 0.5 L per day, based on their 24-hour urine volume and urine osmolality prior to randomization.
Outcomes and Results
While 5 patients in the hydration group and 7 patients in the control group died before the study was concluded, 590 surviving patients received follow-up measurements after one year.
The primary outcome of the study measured changes in estimated glomerular filtration rate (eGFR) from enrollment to one-year after randomization.
The mean change in the hydration and control groups was −2.2 mL/min per 1.73 m2 and −1.9 mL/min per 1.73 m2, respectively. While the mean change in eGFR did not significantly differ between the hydration group and the control group, the hydration group did have a slightly higher decline in eGFR at the end of the study, with the difference between the groups being −0.3 mL/min per 1.73 m2.
Secondary outcomes in the study measured differences in plasma copeptin concentration, creatinine clearance, urine albumin and quality of health between the hydration group and the control group.
Even though statistically significant differences in plasma copeptin concentration and creatinine clearance were seen between the two groups, urine albumin and quality of health did not noticeably differ. After one year, the change in plasma copeptin concentration was 2.2 pmol/L lower in the hydration group, while the change in creatinine clearance was 3.6 mL/min per 1.73 m2 higher. However, urine albumin only differed 6.8 mg/d between both groups and quality of health only differed 0.2 points on a 0–10 scale.
Could Drinking More Water Slow Kidney Function Decline in CKD Patients?
While coaching patients to drink more water over a 12-month period was not shown to prevent a decline in eGFR in patients participating in the CKD WIT, secondary outcomes suggest that increasing water intake may be able to lower vasopressin secretion in CKD patients.
However, a greater difference in the amount of water consumed between groups may be required to have a noticeable effect on eGFR. In order to detect changes in eGFR, researchers may also need to perform follow-ups more than one year after increasing water intake.
Drinking more water might not slow the decline of kidney function in patients with chronic kidney disease, as previous studies may have been confounded. The CKD WIT may have been underpowered as well, which could have prevented researchers from recognizing an effect that is statistically significant.
