The effects of sarcopenia and obesity on femur neck bone mineral density in elderly Korean men and women

OBJECTIVES: We aimed to clarify the relationship between fat, muscle, and bone in elderly men and women. METHODS: We analyzed 1373 men and 1803 women who were older than 65 years from the 2008–2010 Korea National Health and Nutritional Examination Surveys. Body composition and femur neck bone mineral density (BMD) were measured by dual-energy X-ray absorptiometry. Sarcopenia was defined as an appendicular skeletal muscle index (SMI) below one standard deviation (SD). Obesity was classified by fat mass index (FMI). Osteoporosis was defined as a BMD of 2.5 SD below that of femur neck BMD. RESULTS: SMI and FMI were positively correlated with femur neck BMD. In multiple regression analysis, SMI (β = 0.302 in men, β = 0.154 in women; p < 0.001 each) and FMI (β = 0.079 in men, β = 0.179 in women; p = 0.003 and p < 0.001 respectively) had a positive relationship with femur neck BMD. Men with sarcopenia were 3.89 times more likely to develop osteoporosis. Women with sarcopenia were 1.87 times more likely to develop osteoporosis. Sarcopenia was more clinically significant in the development of osteoporosis in men with a fat deficit and women with excess fat. CONCLUSIONS: Muscle mass and fat mass were identified as determinants of femur neck BMD in men and women. Among them, muscle mass of men and fat mass of women are the most important determinants of femur neck osteoporosis.