Higher serum ferritin level and lower femur neck strength in women at the stage of bone loss (≥ 45 years of age): The Fourth Korea National Health and Nutrition Examination Survey (KNHANES IV)

Purpose: Despite the clear effect of iron on bone metabolism, most clinical studies related to bone health have only focused on bone mineral density (BMD). In the present study, we investigated the relationship between serum ferritin and composite indices of femur neck strength via a population-based, cross-sectional study using the Korea National Health and Nutrition Examination Survey (KNHANES). Methods: Our study series included 693 women at the stage of bone loss (>= 45 years of age), defined based on the observed patterns of age-related BMD changes in the KNHANES. Geometric bone structure properties, including hip axis length (HAL) and femur neck width (FNW), were measured using hip dual-energy X-ray absorptiometry scans and were combined with BMD, body weight, and height to create composite indices of femur neck strength relative to load in three different failure modes: compression (CSI), bending (BSI), and impact strength indices (ISI). Results: After adjustment for age, body mass index (BMI), lifestyle factors, serum 25-hydroxyvitamin D, calcium and phosphorus intake, diabetes, and menopause status, multiple regression analyses revealed that serum ferritin was inversely associated with the BMD values at the lumbar spine and femur neck, and the femur neck cortical thickness. Importantly, in all adjustment models, higher serum ferritin was consistently associated with the lower values for all three femur neck composite indices, such as CSI, BSI, and ISI. Conclusions: These data provide the first clinical evidence that increased total body iron stores reflected by higher serum ferritin may be associated with the decrease of bone strength relative to load.