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.