To determine the effect of four vitamin D supplement doses on falls risk in elderly nursing home residents.

DESIGN: Secondary data analysis of a previously conducted randomized clinical trial.

SETTING: Seven hundred twenty-five-bed long-term care facility.

PARTICIPANTS: One hundred twenty-four nursing home residents (average age 89).

INTERVENTION: Participants were randomly assigned to receive one of four vitamin D supplement doses (200 IU, 400 IU, 600 IU, or 800 IU) or placebo daily for 5 months.

MEASUREMENTS: Number of fallers and number of falls assessed using facility incident tracking database.

RESULTS: Over the 5-month study period, the proportion of participants with falls was 44% in the placebo group (11/25), 58% (15/26) in the 200 IU group, 60% (15/25) in the 400 IU group, 60% (15/25) in the 600 IU group, and 20% (5/23) in the 800 IU group. Participants in the 800 IU group had a 72% lower adjusted-incidence rate ratio of falls than those taking placebo over the 5 months (rate ratio=0.28; 95% confidence interval=0.11-0.75). No significant differences were observed for the adjusted fall rates compared to placebo in any of the other supplement groups.

CONCLUSION: Nursing home residents in the highest vitamin D group (800 IU) had a lower number of fallers and a lower incidence rate of falls over 5 months than those taking lower doses. Adequate vitamin D supplementation in elderly nursing home residents could reduce the number of falls experienced by this high falls risk group.