Vitamin D deficiency among older women with and without disability.

BACKGROUND: Vitamin D deficiency is associated with bone loss and bone fractures, and the identification of vulnerable populations is important to clinical practice and public health.
OBJECTIVE: The objectives of this study were to determine the prevalence of vitamin D deficiency and to examine associated risk factors for vitamin D deficiency in older women.
DESIGN: We measured serum concentrations of 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1, 25(OH)(2)D], intact parathyroid hormone (PTH), osteocalcin, and ionized calcium in women aged >/=65 y who were participating in the Women's Health and Aging Study I, an observational study of women representing the approximately one-third most disabled women living in the community, and women aged 70-80 y who were participating in the Women's Health and Aging Study II, an observational study of women among the two-thirds least disabled women living in the community in Baltimore.
RESULTS: The women were classified into 4 domains of physical disability. Among 371 women with 0 or 1 domain of disability and 682 women with >/=2 domains of disability, 6.2% and 12.6%, respectively, had vitamin D deficiency [serum concentrations of 25(OH)D < 25 nmol/L]. In univariate analyses, risk factors for vitamin D deficiency included increasing age, black race, low educational level, high body mass index, high triceps skinfold thickness, increasing level of disability, winter season, and elevated creatinine concentration. In multivariate models, black race had a strong association with vitamin D deficiency when other risk factors were adjusted for.
CONCLUSIONS: Vitamin D deficiency, a preventable disorder, is a common and important public health problem for older disabled women living in the community; black women are at higher risk than are white women.