MON-387 Association Between Vitamin D Level and Bone Mineral Density in Korean Adolescents

Introduction Fractures are common in pediatric population, and lower bone density increases the risk of fracture. Most bone acquisition happens during youth, so juvenile bone mineral density (BMD) assessment is important. There are many factors associated with low BMD, including vitamin D status, calcium intake, low body weight, and physical activity. Among these, our investigation focused on the association of BMD with vitamin D in adolescents. Methods This study investigated data of 1,063 adolescents aged 12-18 years from the fifth and sixth Korea National Health and Nutritional Examination Survey (2009-2011). The association of various factors (vitamin D level, calcium intake, body mass index (BMI), lean mass, fat mass, and physical activity) with BMD Z-scores in whole body, lumbar spine, total femur, and femur neck were analyzed. We defined vitamin D deficiency (≤ 12 ng/mL), vitamin D insufficiency (12-20 ng/mL), and sufficiency (> 20ng/mL) according to the 25-hydroxyvitamin D (25-OHD) level. We analyzed association between BMD and vitamin D levels after adjusting for other factors. Results The mean 25-OHD level of subjects was low (16.28 ng/ml). Of all subjects, 21.9% were vitamin D deficient, and 58.5% were vitamin D insufficient. Among the vitamin D groups, the vitamin D sufficient group had significantly higher BMD Z-scores than the vitamin D deficient group in whole body, lumbar spine, and femur neck. The sufficient vitamin D group had higher BMD Z-score than the vitamin D insufficient group in femur neck, and the vitamin D insufficient group had higher BMD Z-score than the vitamin D deficient group in whole body. Among various factors, vitamin D status, calcium intake, BMI, lean mass, fat mass, and physical activity were positively associated with BMD Z-scores. In particular, lean mass was the strongest independent factor. Vitamin D levels were positively associated with the BMD Z-scores even after adjusting for other factors. Conclusions Vitamin D deficiency and insufficiency were common among adolescents. This study suggested that vitamin D level was positively associated with BMD, and that sufficient vitamin D level was needed to prevent low BMD. Vitamin D status is an important factor of BMD in adolescents.