Vitamin D deficiency in elderly women in nursing homes: investigation with consideration of decreased activation function from the kidneys.

OBJECTIVES: To determine the approximate percentage of women in nursing homes who have vitamin D deficiency and to investigate whether, in assessing vitamin D status in elderly women, there are problems with measuring only 25 hydroxy-vitamin D(3) (25(OH)D(3) ) and whether decreased vitamin D activation as a result of poor renal function needs to be considered.
DESIGN: Cross-sectional study.
SETTING: Forty-eight nursing homes in Japan. PARTICIPANTS: Four hundred three women with a mean age of 86.5 living in nursing homes who had participated in a clinical trial for hip protectors and were not bedridden. MEASUREMENTS: At the start of the trial, in addition to general biochemical data, 25(OH)D(3) , 1,25-dihydroxy-vitamin D(3) (1,25(OH)(2) D(3) ), intact parathyroid hormone (intact PTH), calcium (Ca), phosphorus (P), bone alkaline phosphate (BAP), cross-linked N-telopeptide of type I collagen (NTx), and osteocalcin were measured in participants' blood, and statistical analysis was performed.
RESULTS: 25(OH)D(3) , which is thought to reflect vitamin D status in the body, was surveyed and found to have a mean value of 16.7 ng/mL. 25(OH)D(3) was less than 16 ng/mL in 49.1% of all participants. Creatinine clearance (CCr) was less than 30 mL/min in 20.1% of participants. Participants with serum 25(OH)D(3) less than 16 ng/mL and CCr less than 30 mL/min had significantly higher levels of intact PTH and serum NTx. Participants with a CCr less than 30 mL/min had significantly lower levels of 1,25(OH)(2) D(3) .
CONCLUSION: Frail elderly adults living in nursing homes with poor renal function had lower 1,25(OH)(2) D(3) and higher intact PTH levels and were thus thought to have poorer vitamin D activating capacity. Supplementation with cholecalciferol may be insufficient in people who have poor renal function.