Vitamin D deficiency and nutritional status in elderly hospitalized subjects in Iceland

Objective: Poor nutrition and limited sunlight exposure (season) can be related to reduced serum 25-hydroxyvitamin D (25(OH)D) concentrations. Thus, elderly people in the Nordic countries might be at high risk for vitamin D deficiency. The aims of the study were to describe the: prevalence of vitamin D deficiency in elderly hospitalized patients in Reykjavik, Iceland, and to investigate the effects of nutritional status and season on serum 25(OH)D. Design: Cross-sectional study. Nutritional status was assessed and fasting blood was drawn and analysed for serum 25(OH)D and other clinical routine measurements. Setting: Departments of Geriatrics, Landspitali-University Hospital, Reykjavik, Iceland. Subjects: Sixty hospitalized patients (mean age 83.0 (SD 7.9) years) were randomly assigned. Results: Of the patients, 12.3% Suffered from vitamin D deficiency (serum 25(OH)D < 25 nmol/l) and 71.9% suffered from hypovitaminosis D (serum 25(OH)D = 25-75 nmol/l). There were no significant effects of gender or nutritional status on serum 25(OH)D. Anthropometric variables correlated significantly with serum 25(OH)D, but on stepwise linear regression modelling for the prediction of serum 25(OH)D, BMI remained the only predictor variable (B= -1.454, 95% CI -2.535, -0.373, P=0.009). Conclusions: BMI was significantly negatively associated with serum 25(OH)D in hospitalized elderly patients. Neither nutritional status nor season significantly affected serum 25(OH)D in our patient group. Higher levels of serum 25(OH)D in elderly subjects with lower BMI are most likely explained by volume of distribution rather than by mobilization of vitamin D from its storage in adipose tissue clue to age and disease-related catabolism.