How would you frame the take-home message of the study?

  • Over an 11 year period (1998-2000 to 2009-2011), average serum concentration of 25-hydroxyvitamin D (25OHD) increased 16.2 nmol/L (6.5 ng/mL) in a cohort of midlife women followed longitudinally through the Study of Women’s Health Across the Nation (SWAN). The absolute increase in 25OHD was very similar among women of differing race and ethnicity, educational attainment, and socioeconomic status. Increasing prevalence of the use of vitamin supplements appeared to underlie the observed increases.

What are the clinical implications of the findings?

  • Accumulating evidence suggests that women with a 25OHD less than 30 nmol/L (12 ng/ml) are at increased risk of osteoporosis and may benefit from vitamin D supplementation. The prevalence of 25OHD below this threshold dropped from 20.4 to 9.7% of the cohort. Our data suggest that increased awareness of the importance of vitamin D among both physicians and patients has dramatically decreased the number of women at high risk of complications of low vitamin D. However, the number of women at high risk is still substantial. In particular, 23% of women in our cohort who did not take vitamin supplements had a 25OHD less than 12 ng/mL, and among Black women not taking supplements, the prevalence was 46%.

What kind of research is needed moving forward?

  • Ideally, further educational outreach efforts as well as clinical trials studying the effects of vitamin D supplementation should target those patients at highest risk of complications of vitamin D deficiency. Our data help to identify some of the risk factors among midlife women; future studies to replicate and extend these findings are warranted.

Authors: Mitchell DM, Ruppert K, Udupa N, Bassir F, Darakananda K, Solomon DH, Lian Y, Cauley JA, Karlamangla AS, Greendale GA, Finkelstein JS, Burnett-Bowie SM.