Determinants of Vitamin D Levels in Nursing Home Residents

Objective

To determine the effect of various doses of vitamin D₂ and D₃, as well as ambulatory status (a surrogate for sun exposure), on 25-OH-D levels.

Design

Cross-sectional study with multiple regression analysis.

Setting

A state veterans home for veterans and their spouses.

Participants

Three hundred two of 609 eligible residents.

Measurements

Serum 25-OH-D and parathyroid hormone (PTH) level, supplemental dose of vitamins D₂ and D₃ per kilogram of body weight, and 3 levels of ambulatory status.

Results

The mean 25-OH-D level was 28.6 + 9.2 ng/mL; 6.6% of subjects had values of 16 ng/mL or below. Thirty-two percent of participants had 25-OH-D levels below 30 ng/mL and PTH elevation based on stage of kidney disease, evidence that the suboptimal 25-OH-D level had physiologic consequences. Residents unable to transfer independently had 25-OH-D levels 1.6 ng/mL lower than those able to transfer independently. A regression analysis performed in residents unable to transfer independently (less likely to be exposed to the sun) demonstrated that the average increase in 25-OH-D level per 100 IU of D₃ in a 70-kg resident was 2.1 ng/mL versus 1.8 ng/mL for vitamin D₂.

Conclusion

Nursing home residents should receive at least 800–1000 IU of D₃ per day in an effort to maintain optimal vitamin D levels.