HealthDay News — Summer levels of serum 25-hydroxyvitamin D (25[OH]D) are associated with bone mineral density (BMD) of the total hip, according to a study published in the Journal of Internal Medicine.

Karl Michaëlsson, MD, from Uppsala University in Sweden, and colleagues examined the relative importance of serum 25(OH)D for BMDy by season in a subcohort of 5002 Swedish women randomly selected from a large population-based cohort.

The researchers found that there was a gradual increase in BMD of the total hip in samples collected during summer, up to a serum 25(OH)D level of 40 nmol L−1. Compared with those with serum 25(OH)D levels above 80 nmol L−1, adjusted BMD was 11% lower in women with serum 25(OH)D concentrations below 30 nmol L−1 and 6% lower in those with serum 25(OH)D concentrations 30 to 40 nmol L−1 during summer. Compared with concentrations above 80 nmol L−1, low serum 25(OH)D concentrations (less than 30 nmol L−1) during summer correlated with increased adjusted relative risk of osteoporosis

There were no differences in mean BMD values between categories of serum 25(OH)D in winter.

“To determine a serum 25(OH)D cut-off level for vitamin D deficiency, it may be necessary to take into account the season of blood collection,” the researchers wrote.

Disclosures: The researchers report no conflicts of interest.

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Reference

  1. Michaëlsson K, Wolk A, Byberg L, Mitchell A, Mallmin H, Melhus H. The seasonal importance of serum 25-hydroxyvitamin D for bone mineral density in older women. J Intern Med. 2016 Sept 25. doi: 10.1111/joim.12563 [Epub ahead of print]