Vitamin D deficiency as the risk of respiratory tract infections in the institutionalized elderly: A prospective 1-year cohort study.

Background & Aims: Respiratory tract infections (RTIs) are one of the major causes of morbidity and mortality in the elderly. Since vitamin D is known to play important roles in immunity, and its deficiency has been reported to be prevalent in the elderly, we have studied the relationship between serum 25-hydroxyvitamin D [25(OH)D] level, which is the most reliable marker for vitamin D status, and the incidence of RTIs in the institutionalized elderly by a prospective observational study.

Methods: From 208 Japanese subjects aged 60 and older fulfilling the inclusion criteria, 148 subjects remained after propensity score matching. Data were obtained from the medical records including their age, gender, histories of co-morbidities and medications, the incidence of acute RTIs including pneumonia. Measurement of serum 25(OH)D level and assessment of nutrients intake including vitamin D were done at baseline. Cox's proportional hazard analysis was performed to assess the significant predictors for RTIs during the follow-up period.

Results: The median observation duration was 354.2 days, and the incidence of RTIs was 75.8 person-years. Subjects with RTIs had significantly lower serum 25(OH)D concentration, and a higher prevalence of vitamin D deficiency (25(OH)D < 10 ng/mL). Cox's proportional hazard analysis revealed that vitamin D deficiency was a significant predictor for RTIs.

Conclusions: Our results suggested that vitamin D deficiency was a significant predictor for an increased incidence of RTIs in institutionalized elderly, and the necessity of vitamin D supplementation for the prevention of RTIs was considered.