Association between prehospital vitamin D status and incident acute respiratory failure in critically ill patients: a retrospective cohort study

OBJECTIVE: We hypothesise that low 25-hydroxyvitamin D (25(OH)D) levels before hospitalisation are associated with increased risk of acute respiratory failure. DESIGN: Retrospective cohort study. SETTING: Medical and Surgical Intensive care units of two Boston teaching hospitals. PATIENTS: 1985 critically ill adults admitted between 1998 and 2011. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The exposure of interest was prehospital serum 25(OH)D categorised as ≤10 ng/mL, 11–19.9 ng/mL, 20–29.9 ng/mL and ≥30 ng/mL. The primary outcome was acute respiratory failure excluding congestive heart failure determined by International Classification of Diseases Ninth Edition (ICD-9) coding and validated against the Berlin Definition of acute respiratory sistress syndrome. Association between 25(OH)D and acute respiratory failure was assessed using logistic regression, while adjusting for age, race, sex, Deyo-Charlson Index and patient type (medical vs surgical). In the cohort, the mean age was 63 years, 45% were male and 80% were white; 25(OH)D was ≤10 ng/mL in 8% of patients, 11–19.9 ng/mL in 24%, 20–29.9 ng/mL in 24% and ≥30 ng/mL in 44% of patients. Eighteen per cent (n=351) were diagnosed with acute respiratory failure. Compared to patients with 25(OH)D ≥30 ng/mL, patients with lower 25(OH)D levels had significantly higher adjusted odds of acute respiratory failure (≤10 ng/mL, OR=1.84 (95% CI 1.22 to 2.77); 11–19.9 ng/mL, OR=1.60 (95% CI 1.19 to 2.15); 20–29.9 ng/mL, OR=1.37 (95% CI 1.01 to 1.86)). CONCLUSIONS: Prehospital 25(OH)D was associated with the risk of acute respiratory failure in our critically ill patient cohort.