Effect of vitamin D supplementation on the clinical conditions in the institutionalized elderly subjects

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Pneumonia is a common cause of death among older people despite the availability of potent new antimicrobials. Vitamin D (VD) deficiency is especially common in institutionalized elderly people probably due to limited sun-exposure, skin diseases and problems of dietary intake and is associated with hip fractures and higher mortality from life-threatening conditions such as cardiovascular diseases, cancer and diabetes mellitus. Recently, 1,25-dihydroxyvitamin D, a biologically active form of VD, was reported to be a potent immune modulator of the adaptive immune system and to stimulate the innate immune response upon infection. The aim of the first study was to examine whether VD deficiency correlates with depressed cellular immunity and increases susceptibility to respiratory tract infections among older residents of long-term care facilities. We measured serum concentrations of 1,25-dihydroxyvitamin D and albumin, performed a tuberculin skin test, an indicator of cellular immunity and assessed retrospectively the incidence of both febrile respiratory illnesses and pneumonia. In the first study we showed that a lower serum level of 1,25-dihydroxyvitamin D correlated with a depressed tuberculin response and an increased susceptibility to respiratory tract infections in the institutionalized elderly subjects. In the second study, we performed a prospective study to determine the effect of VD supplementation on the febrile respiratory illnesses in frail elderly people who often have low serum VD levels and are at high risk for pneumonia. As a result, we could find no significant effects in the VD supplementation in institutionalized frail elderly subjects.