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 D3 (25(OH)D3) 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)D3, 1,25‐dihydroxy‐vitamin D3 (1,25(OH)2D3), 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)D3, 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)D3 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)D3 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)2D3. Conclusion Frail elderly adults living in nursing homes with poor renal function had lower 1,25(OH)2D3 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.