<qa>  What is the fourth leading cause of death in institutionalized elderly people in Japan?Pneumonia is the fourth leading cause of death and frequently occurs in institutionalized elderly people in Japan. Recently, several clinical and experimental studies have reported the importance of vitamin D in the regulation of immune functions and its deficiency is associated with susceptibility to some infections. In the present study, the investigators hypothesize that deficiency of serum vitamin D is associated with development of pneumonia, and supplementation of vitamin D may lower the incidence of pneumonia and prolong survival in institutionalized elderly subjects. 