TUESDAY, Oct. 4, 2016 (HealthDay News) — Summer levels of serum 25-hydroxyvitamin D (S-25OHD) are associated with bone mineral density of the total hip, according to a study published online Sept. 25 in the Journal of Internal Medicine.
Karl Michaëlsson, M.D., from Uppsala University in Sweden, and colleagues examined the relative importance of S-25OHD for bone mineral density by season in a subcohort of 5,002 Swedish women randomly selected from a large population-based cohort.
The researchers found that there was a gradual increase in bone mineral density of the total hip in samples collected during summer, up to an S-25OHD level of 40 nmol L−1. Compared to those with S-25OHD levels above 80 nmol L−1, adjusted bone mineral density was 11 percent lower in women with S-25OHD concentrations below 30 nmol L−1 and 6 percent lower in those with S-25OHD concentrations 30 to 40 nmol L−1 during summer. Compared with concentrations above 80 nmol L−1, low S-25OHD concentrations (<30 nmol L−1) during summer correlated with increased adjusted relative risk of osteoporosis. There were no differences in mean bone mineral density values between categories of S-25OHD in winter.
“To determine an S-25OHD cut-off level for vitamin D deficiency, it may be necessary to take into account the season of blood collection,” the authors write.
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