Association between serum calcium and 28-day mortality in critically ill patients with COVID-19: A retrospective cohort study from MIMIC-IV database

Although serum calcium levels are associated with the prognosis of various critical illnesses, their specific relationship with 28-day mortality in critically ill patients with coronavirus disease 2019 (COVID-19) remains unclear. This relationship has potential implications for patient management and prognosis assessment. This investigation examines the association between serum calcium concentrations and 28-day mortality among severely ill patients with COVID-19. This retrospective cohort analysis encompassed 806 intensive care unit admitted COVID-19 patients, utilizing data extracted from the Medical Information Mart for Intensive Care - IV (MIMIC-IV) 3.0 database. Information regarding vital signs, laboratory test results, and preexisting conditions was compiled to explore the association of serum calcium concentrations with 28-day mortality. This study comprised 806 critically ill COVID-19 patients, averaging 64 years of age, of which 59% were male. The 28-day mortality rate for this cohort was 27.7%. Preliminary analyses indicated a strong relationship between elevated serum calcium levels at admission and a lower 28-day mortality rate (hazard ratio [HR] = 0.71; 95% confidence interval [CI] = 0.61-0.82; P < .001). Following adjustment for various confounding factors, the correlation between serum calcium concentrations and decreased 28-day mortality retained statistical association (HR = 0.83, 95% CI = 0.71-0.97, P = .021). Stratification of calcium concentrations into tertiles showed that patients in the top tertile (T3) exhibited a markedly decreased risk of 28-day mortality versus individuals within the bottom tertile (T1) (model III: HR = 0.70, 95% CI = 0.50-0.99, P = .043). Subgroup assessments showed comparable results across distinct demographic groups. Elevated serum calcium concentrations at the time of admission were linked to a reduced 28-day mortality in critically ill patients with COVID-19, offering a new perspective on the role of calcium in the management and prognosis of COVID-19.