The Association between Dehydroepiandrosterone Sulfate (DHEA-S) and Bone Mineral Density in Korean Men and Women

BACKGROUND: The relationship between dehydroepiandrosterone sulfate (DHEA-S) and bone mineral density (BMD) is controversial. And findings of most studies that have investigated this relationship are restricted to postmenopausal women. In this study, we investigated the relationship between serum DHEA-S and BMD in both men and women. METHODS: This cross-sectional study evaluated a total of 294 healthy Korean participants through a medical examination program. And a subgroup of 154 participants was subjected to a longitudinal analysis. We measured BMD by dual energy X-ray absorptiometry and assayed DHEA-S by a chemiluminescent immunoassay. RESULTS: We evaluated the association between serum DHEA-S concentration and BMD at the femur trochanter after adjusting for cofounders such as age, body mass index, lifestyle factors, serum cortisol level, serum insulin-like growth factor 1 (IGF-1) level, and sex. Through our longitudinal study, we found that the changes in BMD at the total spine, at the femur neck, and at the femur trochanter were all smaller in the ΔDHEA-S 0 group. CONCLUSIONS: We found that there was a positive correlation between serum DHEA-S and femur BMD, which suggests that controlling serum DHEA-S levels may retard age-related BMD reduction in Koreans.

Effects of Age and Sex on the Electromyographic Reaction Time of Tibialis Anterior Muscle Contraction

OBJECTIVE: Compared to elderly men, elderly women have substantially reduced performance of postural balance and greater risk of falls. To investigate the effect of age and sex on electromyographic (EMG) reaction time of tibialis anterior muscle contraction. METHOD: Fifty-nine elderly subjects and 29 young subjects participated in this study. Subjects were instructed to dorsiflex the ankle of the dominant leg as forcefully and quickly as possible in response to audible beeps. EMG activity was recorded over the tibialis anterior muscle and delays in initiation and termination of EMG signal were measured by two examiners. Mean and intrasubject variability of each delay were used as outcome measures. RESULTS: Both the intra-examiner and inter-examiner reliability of delay variables were above 0.97. Delays in initiation and termination of muscle contraction, as well as their intrasubject variability, were significantly greater in the elderly (p<0.01). However, there were no sex differences or interaction in all outcome measures. CONCLUSION: These results demonstrate that the EMG reaction time and their variability increase in the elderly population with no sex difference.