The Reference Value of Skeletal Muscle Mass Index for Defining the Sarcopenia of Women in Korea

BACKGROUND Sarcopenia is considering important disease entity in elderly. Several study groups define the sum of the muscle masses of the four limbs as appendicular skeletal mass (ASM) to calculate skeletal muscle index (SMI). The purpose of this study was to determine cut point of SMI for sarcopenia in Korean women. METHODS This study was based on data obtained from the 2008 to 2011 Korean National Health and Nutrition Examination Survey (KNHANES) IV and V. A whole body dual energy X-ray absorptiometry scan were performed on individuals of ≥10 years old from July 2008 to May 2011. In the analysis, 11,633 women were included. ASM was calculated and SMI was obtained as ASM/height(2). Cutoff value was defined two standard deviations below mean values for young reference group. RESULTS Of 11,633 women aged 10 to 97 years, mean and standard deviation of year was 46.73±18.54 years. The highest level of height was noted in 20's and the highest total sum of skeletal mass was seen 14.87 kg in 40's. The highest value of SMI was noted in 60's in Korean women. Cutoff value as mean value of young women was decided with SMI of 30's and 40's that have peak ASM. Mean and standard deviation of SMI in those ages was 5.9±0.7 kg/m(2). A SMI of two standard deviations below the mean SMI of reference groups was 4.4 kg/m(2) as cutoff value. CONCLUSIONS This study shows that 4.4 kg/m(2) of SMI in Korean women was cutoff value of sarcopenia. Further study is clearly required to decide cutoff value of SMI for sarcopenia, especially for Korean women.