Mitchell DM, et al. - In this study involving 1,585 racially, ethnically, and socioeconomically diverse midlife women, researchers assessed mean 25(OH)D changes over time and their determinants. Serum 25(OH)D levels were measured at two time points: 1998-2000 and 2009-2011. According to findings, temporary increases in 25(OH)D concentrations are largely driven by increased use of supplements among midlife women. The proportion of women with 25(OH)D levels < 30 nmol/L (and thus at high risk for skeletal consequences) remains significant. The investigators advised targeted vitamin D deficiency screening in populations at risk for fragility fracture.