The Association of Vitamin D With Femoral Neck Strength: An Additional Evidence of Vitamin D on Bone Health

Context: Although bone mineral density (BMD) is a strong predictor of fracture risk, additional parameters, such as bone strength, are needed to predict future fracture risk because of the low sensitivity of BMD for predicting fracture risk. Objective: The objective was to study the association of vitamin D with femoral neck (FN) strength. Design and Setting: This was a population-based, cross-sectional study from Korea National Health and Nutrition Examination Surveys. Participants: A total of 1209 Koreans (586 men and 623 women) aged >= 50 years participated. Main Outcome Measures: We calculated composite indices of FN strength, such as the compression strength index, bending strength index (BSI), and impact strength index, by combining BMD, body weight, and height with the femoral axis length and width, which were measured by dual-energy x-ray absorptiometry. Results: Multiple regression analysis demonstrated that serum 25-hydroxyvitamin D [25(OH)D] levels were associated with compression strength index, BSI, and impact strength index in both genders. When women were categorized into four quartiles of 25(OH)D, FN BMD and composite indices (except for BSI) significantly increased from the lowest (Q1) to the highest quartile (Q4) (P for trend = .001-.004). In contrast, there is no significant association of quartiles with composite indices in men. When women were divided into two groups according to their serum 25(OH)D levels, the composite indices as well as the FN BMD were markedly higher in subjects with higher 25(OH)D levels (>= 51.5 nmol/L). Conclusion: These findings provide the first clinical evidence that high serum 25(OH)D levels exhibit higher composite indices of FN strength in a dose-dependent manner, especially in women.