Background: Vitamin and mineral supplementation can improve immune function indices; therefore, supplementation may reduce infections, particularly in the nursing home setting, where nutritional deficits are common. Liu and colleagues investigated the clinical impact of vitamin and mineral supplementation in nursing home residents.

The Study: Eligible residents from 21 nursing homes were randomly assigned to receive multivitamin supplementation or placebo for 19 months. A dietitian recorded each participant's baseline nutritional status. A certified practitioner performed infection-control surveillance for 18 months, allowing for a one-month run-in period. Skin, soft tissue, upper and lower respiratory, gastrointestinal, urinary, and hematologic infections were monitored. The primary outcome was number of infections per participant; secondary outcomes were antibiotic use and hospitalization rate.

Results: Of 2,645 eligible residents, 748 were included in the intention-to-treat analysis; most participants were women. Baseline characteristics were similar between the intervention and placebo groups, except for a higher rate of dementia in the intervention group. The mean number of infections per participant was 1.66, with a total of 1,245 infections (3.7 per 1,000 resident-days). The difference in infection rate between the groups was not statistically significant: 583 in 375 participants (3.5 per 1,000 resident-days) in the intervention group and 662 in 373 participants (3.8 per 1,000 resident-days) in the placebo group. Univariate analysis showed fewer antibiotic days in the supplement group than in the placebo group, and there was no difference in hospitalization rates between the two groups. A multivariate model showed no differences between groups. Dementia was the only baseline characteristic that affected infection rate. Post-hoc subgroup analysis showed that in the intervention group, patients without dementia had a lower rate of infection compared with those in the placebo group.

Conclusion: Overall, multivitamin supplementation did not reduce the number of infections in nursing home residents. A decrease in the number of antibiotic days in residents receiving supplementation warrants further analysis. Nursing home residents without dementia may benefit from supplementation.

editor's note: There is little support for using multivitamins to prevent infections in the general population, regardless of age. A trial of multivitamin supplementation in older adults living at home found no difference in any of the outcome measures.¹ In the nursing home setting, there may be specific subgroups of sicker patients who benefit from supplementation, as suggested by the trial conducted by Liu and colleagues. Although unproven, one reason patients without dementia were found to be more vulnerable to infection than those with dementia may be that physical conditions requiring long-term care are more debilitating and associated with a higher degree of comorbidity than cognitive deficits. The need to identify subgroups is supported by another trial of multivitamin supplementation in adults.² The intervention group had fewer infections, but most patients in this group who benefited had diabetes.² It seems reasonable to offer vitamin supplementation to sicker, malnourished, or immunocompromised patients as a means of preventing infection, but not as a routine preventive measure.—c.w.