Bone Abstracts

Discordance of T-score is frequently observed and affects to therapeutic strategy in osteoporosis. Z-score discordance in premenopausal women has not been reported yet. In addition, despite of important role of low bone mineral density (BMD) in premenopausal women to predict osteoporotic fracture in postmenopausal age, there are very few reports on the status of low BMD in healthy premenopausal women. To investigate the current status of idiopathic osteoporosis and contributing factors to low BMD in addition to the presence of Z-score discordance in healthy premenopausal women. The Fourth Korea National Health and Nutrition Examination Surveys (KNHANES IV) conducted in 2008–2009. Total 3003 premenopausal women aged 18–50 years without secondary causes of low BMD were included. The prevalence of low BMD in healthy premenopausal women was 2.8%. BMI, total body muscle mass and supplemental amount of calcium and vitamin D were associated with low BMD. By analyzing spine and femur separately, risk factors were different depending on the site; low BMI and vitamin D deficiency were risk factors of low femur neck (FN) BMD, but not of low lumbar spine (LS) BMD. Discordance of Z-score was observed, the prevalence is more than 75%, and major discordance of Z-score was found in 40.9 and 26.2% of the low LS BMD and low FN BMD groups, respectively. Although different definition was applied, major discordance was much higher than expected in Korean. The risk factors were different depending on the site. Long term follow-up design is needed on the subsequent effect of existing Z-score discordance on the fracture risk.