The Prevalence, Risk Factors, and Clinical Outcomes of Vitamin C Deficiency in Adult Hospitalised Patients: A Retrospective Observational Study

<b>Background/Objectives</b>: Assessment of vitamin C status rarely occurs in hospital patients within high-income countries on the assumption that vitamin C deficiency (VCD) is rare, and evidence on prevalence, risk factors, and clinical outcomes of VCD is limited. This study aimed to describe the prevalence of VCD, characteristics of patients with VCD, and identify risk factors and clinical outcomes associated with VCD status in adult hospitalised patients. <b>Methods</b>: This retrospective observational study included adult inpatients from five metropolitan hospitals within a single public health service in Australia which provides tertiary, acute, and sub-acute care, over a 3.5-year period. Non-fasting vitamin C levels were examined for the prevalence of VCD, defined as <11.4 µmol/L. Multivariate regression models were used to identify risk factors and clinical outcomes associated with VCD. <b>Results</b>: The prevalence of VCD was 22.9% (n = 1791), comprising 23.2% (n = 1717) and 16.2% (n = 74) within acute and sub-acute settings, respectively. VCD prevalence was high in acute setting subgroups including patients with malnutrition (30%, n = 611) and patients admitted to ICU during hospitalisation (37.3%, n = 327). Malnutrition (OR 1.50, 95% CI 1.19-1.91, <i>p</i> < 0.001) and male gender (OR 1.47, 95% CI 1.17-1.86, <i>p</i> = 0.001) were associated with VCD. VCD was not associated with clinical outcomes including in-hospital death, hospital or intensive care unit LOS, or hospital-acquired complications. <b>Conclusions</b>: VCD exists within adult hospital patients in high-income countries, and early, targeted detection of VCD in this setting is warranted. Further research is needed to explore the impact of VCD on hospital clinical outcomes.