Vitamin D deficiency is associated with reduced mobility after hip fracture surgery: a prospective study

Background: Hip fractures are associated with a high rate of morbidity and mortality, and successful ambulation after surgery is an important outcome in this patient population. Objective: This study aims to determinewhether 25-hydroxyvitamin D [25(OH)D] concentration or the Geriatric Nutritional Risk Index (GNRI) is associated with mortality or rates of walking in a patient cohort after hip fracture surgery. Methods: Patients undergoing hip fracture repair from a multisite study in North America were included. Mortality and mobility were assessed at 30 and 60 d after surgery. Serum albumin, 25(OH)D, and intact parathyroid hormone were measured. Patients were characterized according to 25(OH)D <12 ng/mL, 12 to <20 ng/mL, 20 to <30 ng/mL, or >= 30 ng/mL. GNRI was categorized into major/moderate nutritional risk (<92), some risk (92 to <98), or in good nutritional status (>= 98). Results: Of the 290 patients [aged 82 +/- 7 y, BMI (kg/m(2)): 25 +/- 5], 73% were women. Compared with patients with <12 ng/mL, those with higher 25(OH)D concentrations had higher rates of walking at 30 d (P = 0.031): 12 to <20 ng/mL (adjusted OR: 2.61; 95% CI: 1.13, 5.99); 20 to <30 ng/mL (3.48; 1.53, 7.95); >= 30 ng/mL (2.84; 1.12, 7.20). In addition, there was also greater mobility at 60 d (P = 0.028) in patients with higher 25(OH)D compared with the reference group (<12 ng/mL). Poor nutritional status (GNRI <92) showed an overall trend to reduce mobility (unadjusted P = 0.044 and adjusted P = 0.056) at 30 but not at 60 d. There was no association of vitamin D or GNRI with mortality at either time. Conclusions: Vitamin D deficiency (<12 ng/mL) is associated with reduced ambulation after hip fracture surgery, whereas GNRI also contributes to immobility but is a less reliable predictor. Mechanisms that can explain why vitamin D deficiency is associated with mobility should be addressed in future studies.