Kidney stone prevalence continues to rise but producing 2.5 L of urine daily is associated with a 50%-60% decreased risk of stone recurrence.^1-3 Unfortunately, adherence to fluid intake recommendations for prevention has been limited.⁴ Patients report that their thirst is not sufficient to drive the recommended level of fluid consumption and they forget to drink due to their many competing priorities in daily life. With the majority of US adults owning a smartphone that can connect to digital tools, use of technology is increasingly popular to track a variety of health goals.^5,6 Interest has grown in the potential to leverage mobile, wearable, and connected technologies to improve fluid intake monitoring and support behavior change in this population.⁷ Smartphone applications and connected water bottles to track daily fluid intake volume are commercially available, but little evidence exists concerning their efficacy for modifying behavior to increase fluid intake and urine output or preventing kidney stones.

The sip^IT behavioral intervention is a just-in-time reminder system developed for kidney stone patients who struggle to meet the recommended fluid intake guidelines. It is capable of automatically tracking fluid intake using a connected water bottle and wearing a smartwatch with drinking gesture detection, as well as the ability to manually input drinks using the companion mobile app.⁸ If a periodic fluid intake goal is not met, participants receive a message reminding them to drink. These reminder messages are delivered as multimedia messages and were designed to delight recipients while reactivating their fluid intake goal pursuit. Messages are limited to moments of vulnerability when participants are not on track to reach their fluid intake goal. By making reminder messages lapse contingent, disruptions and burden are reduced.

Figure. Connected water bottle, HidrateSpark Pro. Printed with permission of HidrateSpark.

We have conducted 2 studies on sip^IT in preparation for our ongoing trial. The first study established proof-of-concept for the intervention and suggested that it reduced some common barriers to fluid intake and increased the experience of drinking-related automaticity (ie a key indicator that participants were forming habits for fluid intake).⁸ The second study evaluated mini sip^IT, a reduced-cost version of the intervention using only the connected water bottle and its companion mobile app for self-tracking. Almost all participants (n=26) adhered to the program daily. Critically, a significant increase in 24-hour urine volume was observed after the 1-month intervention.⁹ This study of the mini sip^IT intervention was among the first to indicate that a technology-based behavioral intervention may be capable of significantly increasing 24-hour urine volume in adults, a key component of prevention guidelines that is associated with reduced risk of stone recurrence.^1,2,9,10

Our ongoing National Institute of Diabetes and Digestive and Kidney Diseases-funded sip^IT clinical trial is a randomized control trial working to further examine the impact of the sip^IT behavioral intervention in kidney stone patients. The trial is currently ongoing and aims to enroll 216 participants who will be randomized to sip^IT behavioral intervention or usual care (ie, print materials with education about the guidelines and encouragement to increase fluid intake enough to produce 2.5 L/d of urine). Enrollment is anticipated to conclude in early 2024. The primary outcome of the trial is to assess 24-hour urine volume after 3 months (with intermediate and follow-up assessments at 1 and 12 months). Secondary outcomes include changes in 24-hour urine supersaturations, and habit strength for fluid intake from baseline to the 1-, 3-, and 12-month follow-up assessments. Interested individuals with a history of kidney stones in the past 5 years and no conditions precluding high fluid intake, conditions with high fluid losses, or conditions that preclude ability to collect 24-hour urine sample are being enrolled in the trial. Participants completed a baseline 24-hour urine collection, and those with a volume <2.0 L were eligible for the trial. During baseline, all participants received education (usual care) on increasing fluid intake for prevention of kidney stones. Participants randomized into the sip^IT arm were educated on use of a smartwatch (Fitbit Sense) with a custom app that processes signals from the inertial sensors to detect drinking gestures, the connected water bottle (HidrateSpark Pro, see Figure), and both the Fitbit and Hidrate smartphone apps. Staff trained each participant on tracking fluid intake using the devices and participants were contacted by study staff if data was not being received from the watch, bottle, or smartphone applications for >3 days during the study period.

Our clinical trial and the ongoing Prevention of Urinary Stones With Hydration (PUSH) clinical trial are 2 recent National Institutes of Health–funded clinical trials to determine if behavioral intervention technologies can be efficacious for increasing urine volume and reducing risk for kidney stone recurrence. Future studies will aim to assess whether behavior change has led to habit formation and whether high fluid intake for stone prevention persists once the technology is discontinued. We look forward to results from these clinical trials to better understand how behavioral science can improve adherence to fluid intake goals for stone prevention.

Interested readers can find publications from our work and patient-oriented educational materials from the sip^IT trial online at: https://davideconroy.weebly.com/fluid-intake.html

Funding: National Institute of Diabetes and Digestive and Kidney Diseases (R01 DK124469).