Background: We conducted a single-center historical cohort study to evaluate the association between admission serum ionized calcium and mortality in hospitalized patients.
Methods: We included hospitalized patients from January 2009 to December 2013 who had available serum ionized calcium at the time of admission. We assessed the in-hospital and 1-year mortality risk based on admission serum ionized calcium using multivariate logistic and Cox proportional hazard analysis, respectively. To test non-linear association, we categorized serum ionized calcium into six groups; ≤4.39, 4.40-4.59, 4.60-4.79, 4.80-4.99, 5.00-5.19, ≥5.20 mg/dL and selected serum ionized calcium of 4.80-4.99 mg/dL as a reference group.
Results: We studied a total of 33,255 hospitalized patients. The mean admission serum ionized calcium at 4.8 ± 0.4 mg/dL. Hospital and 1-year mortality observed in 1,099 (3%) and 5,239 (15.8%), respectively. We observed a U-shaped association between admission serum ionized calcium and in-hospital and 1-year mortality. Ionized calcium lower threshold for increased in-hospital and 1-year mortality rates was ≤4.59 and ≤4.39 mg/dL, respectively. Ionized calcium upper threshold for increased in-hospital and 1-year mortality rates was ≥5.20 mg/dL.
Conclusion: Both hypocalcemia and hypercalcemia were associated with increased short- and long-term mortality with a U-shape relationship.
Keywords: Ionized calcium; calcium; hospitalization; mortality; outcomes.