High Prevalence of Vitamin D Deficiency in Critically Ill Patients in Tropical Southern Taiwan: Risk Factors and Clinical Outcomes

Objective: Vitamin D deficiency is a global concern, but its prevalence in critically ill patients in high-sunlight tropical regions is limited. This study evaluated the prevalence of vitamin D deficiency in intensive care unit (ICU) patients in southern Taiwan and identified which variables correlate with deficiency and in-hospital mortality. Methods: We prospectively enrolled 221 critically ill patients, categorizing them by serum 25(OH)D levels as follows: Group A (sufficient, ≥30 ng/mL), Group B (insufficient, 20.0–29.9 ng/mL), and Group C (deficient, ≤19.9 ng/mL). Clinical variables, laboratory parameters, and outcomes were analyzed. Results: Despite the tropical climate, 33.5% of patients were vitamin D-deficient, and 47.1% were insufficient. Group C patients were significantly younger than other groups (p = 0.049). Significant differences between Groups C and A were observed in ICU length of stay (p = 0.036) and total hospital stay (p = 0.004). Multivariable analysis confirmed that only younger age (OR 0.968, p = 0.008) and low albumin level (OR 0.171, p < 0.001) were independently associated with vitamin D deficiency. Only serum albumin (p = 0.001) and C-reactive protein (CRP) levels (p = 0.015) were significantly associated with in-hospital mortality. Conclusions: Vitamin D deficiency is highly prevalent among critically ill patients in southern Taiwan, challenging the assumption that tropical ultraviolet exposure is naturally protective. Younger age and hypoalbuminemia are independent predictors of vitamin D deficiency. However, vitamin D levels were not independently associated with in-hospital mortality, which was instead predicted by albumin and CRP levels. These findings highlight a high rate of hypovitaminosis D in ICU but do not support its role as an independent predictor of mortality.