Effect of Multivitamin and Mineral Supplementation on Episodes of Infection in Nursing Home Residents: A Randomized, Placebo-Controlled Study

OBJECTIVES: To evaluate the effect of vitamin and mineral supplementation on infections in an elderly institutionalized population. DESIGN: Eighteen-month, randomized, placebo-controlled trial. SETTING: Twenty-one long-term care facilities. PARTICIPANTS: Seven hundred sixty-three subjects from 21 long-term care facilities. INTERVENTION: Participants were randomized to receive one multivitamin and mineral supplementation daily or placebo. MEASUREMENTS: The primary outcome was number of infections per subject. Secondary outcomes were antibiotic use and hospitalization rates. Infection control surveillance was conducted over 18 months using standardized criteria. RESULTS: Outcome data from 748 subjects, mean age 85, were included in the intention-to-treat analysis. Using univariate analyses, there was no difference in infectious episodes between the supplemented and placebo groups (3.5 infections per 1,000 resident-days vs 3.8 infections per 1,000 resident-days, odds ratio (OR)=0.92, 95% confidence interval (CI)=0.82–1.03, P=.12). There was a reduction in antibiotic usage in the supplementation group, but this was not significant in the multivariate model. There was no difference in the number of hospital visits. In the multivariate analysis, the effect of multivitamin use on total number of infections was not significant (OR=0.77, 95% CI=0.54–1.1). Subjects without dementia had a greater rate of infections than those with dementia (OR=1.44, 95% CI=1.19–1.76). In post hoc subgroup analysis, subjects without dementia who received supplementation had a significantly lower rate of infections than those who received placebo (relative risk=0.81, 95% CI=0.66–0.99). CONCLUSION: Overall, multivitamin and mineral supplementation does not have a significant effect on the incidence of infections in institutionalized seniors, although the subgroup of residents in long-term care without dementia may benefit from supplementation. Further research is needed to determine its effect in high-risk subgroups within the nursing home population.