Association Between Refrigerator Openings and Protein Intake After Hospitalization for Heart Failure Decompensation: Protocol for a Prospective Cohort Pilot Study

Background: Sarcopenia, characterized by loss of muscle mass, reduced strength, and increasing frailty, is common in older adults and is often the result of underlying diseases such as advanced stages of heart failure (HF). Protein intake is crucial for maintaining muscle mass and strength. However, older adults typically consume less protein compared to younger individuals. It has recently been shown that the time of the first refrigerator opening in the morning, indicated by a door sensor, may be correlated with frailty in older individuals living alone. Objective: The aim of this study is to determine whether the time of the first refrigerator opening in the morning can serve as a potential indicator of protein intake in older patients (age ≥70 years) after hospitalization for HF decompensation over a period of 6 months. Methods: This is a substudy of a prospective interventional cohort study that aims to identify changes in digital biomarkers derived from an ambient sensor system, which may support the early detection of HF decompensation. In this substudy, the frequency and timing of refrigerator door openings in participants’ homes will be measured. To assess associations between protein intake and refrigerator openings, dietary intake will be evaluated using 24-hour dietary recalls at 3 different timepoints: at 1, 3, and 6 months after hospital discharge. All 24-hour dietary recalls will be conducted by trained dietitians in face-to-face interviews on weekdays. The primary outcome of this study will be the correlation between protein intake and the time (in minutes after midnight) of the first refrigerator door opening at each of the 3 assessment points. Results: The study is currently in the data collection phase. Recruitment began in February 2024. Data analysis will begin after all data have been collected. As of manuscript submission, 12 patients have been recruited. Results are expected to be published by the end of 2025. Conclusions: Considering that protein-rich foods are typically stored in the refrigerator, the relationship between frailty and refrigerator usage may be a relevant indicator for nutritional assessment, particularly regarding protein intake. In addition, sarcopenia and frailty may also be linked to protein distribution across meals. This study will explore whether monitoring refrigerator openings can serve as a simple method for identifying increased risk of frailty and sarcopenia. Early detection through such monitoring could facilitate timely interventions and potentially reduce the risk of these conditions.