U-shaped association between serum calcium and in-hospital mortality in patients with congestive heart failure

AimsSerum calcium level is widely used for evaluating disease severity, but its impact on clinical outcomes in patients with congestive heart failure (CHF) remains poorly understood. The aim of this study is to investigate the relationship between serum calcium levels and in-hospital mortality in CHF patients.Methods and resultsWe conducted a retrospective analysis utilizing clinical data from the Medical Information Mart for Intensive Care database, encompassing a cohort of 15 983 CHF patients. This cohort was stratified based on their serum calcium levels, with the primary objective being the determination of in-hospital mortality. To assess the impact of admission serum calcium levels on in-hospital mortality, we employed various statistical methodologies, including multivariable logistic regression models, a generalized additive model, a two-piecewise linear regression model, and subgroup analysis. Comparative analysis of the reference group (Q3) revealed increased in-hospital mortality in the first quintile (Q1, the group with the lowest blood calcium level) and the fifth quintile (Q5, the group with the highest blood calcium level), with fully adjusted odds ratios of 1.38 [95% confidence interval (CI): 1.13-1.68, P = 0.002] and 1.23 (95% CI: 1.01-1.5, P = 0.038), respectively. A U-shaped relationship was observed between serum calcium levels and in-hospital mortality, with the lowest risk occurring at a threshold of 8.35 mg/dL. The effect sizes and corresponding CIs below and above this threshold were 0.782 (95% CI: 0.667-0.915, P = 0.0023) and 1.147 (95% CI: 1.034-1.273, P = 0.0094), respectively. Stratified analyses confirmed the robustness of this correlation.ConclusionsOur study identifies a U-shaped association between serum calcium levels and in-hospital mortality in CHF patients, with a notable inflection point at 8.35 mg/dL. Further investigation through prospective, randomized, and controlled studies is warranted to validate the findings presented in this study.