Prevalence of vitamin D inadequacy among postmenopausal North American women receiving osteoporosis therapy

Abstract

Purpose: To evaluate serum 25-hydroxyvitamin D [25(OH)D] con-centrations and factors related to vitamin D inadequacy in postmeno-pausal North American women receiving therapy to treat or prevent osteoporosis. Methods: Serum 25(OH)D and PTH were obtained in 1536 commu-nity-dwelling women between November 2003 and March 2004. Mul-tivariate logistic regression was used to assess risk factors for sub-optimal (30 ng/ml) 25(OH)D. Results: Ninety-two percent of study subjects were Caucasian, with a mean age of 71 yr. Thirty-five percent resided at or above latitude 42 ° north, and 24 % resided less than 35 ° north. Mean (SD) serum 25(OH)D was 30.4 (13.2) ng/ml: serum 25(OH)D was less than 20 ng/ml in 18%; less than 25 ng/ml in 36%; and less than 30 ng/ml in 52%. Prevalence of suboptimal 25(OH)D was significantly higher in subjects who took less than 400 vs. 400 IU/d or more vitamin D. Ther