Vitamin D plays a seminal role in many homeostatic mechanisms. In this study, we assessed the correlation between circulating vitamin D levels and mortality rates in critically ill patients.

All patients admitted to the intensive care units (ICUs) and internal medicine wards in a university-based hospital that required mechanical ventilation were admitted. Data collected included the underlying disease, basic hematological and biochemical blood test results, APACHE II scores and serum 25-hydroxyvitamin D [25(OH)D] levels. The primary end point was defined as all-cause mortality within 60 days from admission or from acute deterioration.

Between December 2008 and June 2009, 130 patients were enrolled. Average vitamin D concentration was 14.04 ± 6.9 ng/ml; 107 patients were vitamin D deficient (< 20 ng/ml). Total mortality rate after 60 days was 44.3%. Vitamin D levels were correlated with white blood cell (WBC) count, but with no other measured variable. Among the deceased patients, survival curves indicated that survival of patients with vitamin D deficiency was significantly shorter than those whose vitamin D concentration was >20 ng/ml (P < 0.05); the average survival time was 15.3 ± 12.4 days for vitamin D deficient patients compared with 24.2 ± 16.5 days among those with normal vitamin D levels.

This study demonstrated that low vitamin D levels are common among patients admitted to ICU. We observed longer survival times among vitamin D sufficient patients. Our results indicate that vitamin D concentration may be either a biomarker of survival or a co-factor. We recommend assessing the effects of vitamin D supplementation in critically ill patients.