Abstract
AIMS: The adverse effects of low daily protein intake (DPI) on clinical outcomes in patients with heart failure (HF) are known; however, an optimal DPI to predict event adverse outcomes remains undetermined. Moreover, whether protein restriction therapy for chronic kidney disease is applicable in patients with HF and renal dysfunction remains unclear. METHODS AND RESULTS: In this single-centre, ambispective cohort study, we included 405 patients with HF aged ≥65 years (mean age, 78.6 ± 7.5 years; 50% women). DPI was estimated from consumption over three consecutive days before discharge and normalized relative to the ideal body weight [IBW, 22 kg/m(2) × height (m)(2)]. The primary outcome was a composite of all-cause mortality and HF-related readmission within the 2 year post-discharge period. RESULTS: During an average follow-up period of 1.49 ± 0.74 years, 100 patients experienced composite events. Kaplan-Meier survival curves revealed a significantly lower composite event-free rate in patients within the lowest quartile of DPI than in the upper quartiles (log-rank test, P = 0.02). A multivariate Cox proportional hazards analysis after adjusting for established prognostic markers and non-proteogenic energy intake revealed that patients in the lowest DPI quartile faced a two-fold higher risk of composite events than those in the highest quartile [hazard ratio (HR), 2.03; 95% confidence interval (CI), 1.08-3.82; P = 0.03]. The composite event risk linearly increased as DPI decreased (P for nonlinearity = 0.90), with each standard deviation (0.26 g/kg IBW/day) decrease in DPI associated with a 32% increase in composite event risk (HR, 1.32; 95% CI, 1.10-1.71; P = 0.04). There was significant heterogeneity in the effect of DPI, with the possible disadvantage of lower DPI in patients with HF with cystatin C-based estimated glomerular filtration rate <30 mL/min/1.73 m(2). The cutoff value of DPI for predicting the occurrence of composite events calculated from the Youden index was 1.12 g/kg IBW/day. Incorporating a DPI < 1.12 g/kg IBW/day into the baseline model significantly improved the prediction of post-discharge composite events (continuous net reclassification improvement, 0.294; 95% CI, 0.072-0.516; P = 0.01). CONCLUSIONS: Lower DPI during hospitalization is associated with an increased risk of mortality and HF readmission independent of non-proteogenic energy intake, and the possible optimal DPI for predicting adverse clinical outcomes is >1.12 g/kg IBW/day in older patients with HF. Caution is warranted when protein restriction therapy is administered to older patients with HF and renal dysfunction.