## 4 Discussion  
The bones function to mechanically support the body and protect deep organs. They become the center of exercise and serve as a reservoir of various minerals. Bones continuously develop throughout the growth period, until the age of 30 to 40 years when the structural growth of the bone is completed. Therefore, BMD continues to increase throughout growth, resulting in peak bone mass and solidification at the end of structural development. The most common metabolic bone disease, osteoporosis, is a condition of reduced BMD. Osteoporosis is a serious metabolic disease accompanied by qualitative changes in bone microstructure and can lead to fractures of the spine, femur, and radius. Patients suffering from osteoporosis are at risk of bone fractures, even from less forceful impact to the bones [20]. Although osteoporosis is more common in women, previous studies have reported that osteoporoporotic fractures are also frequent in men [21,22]. Osteoporosis, therefore, should be recognized as a major disease that affects both women and men. Based on this rationale, this study analyzed the relationship between BMC and age in adults to examine changes in bone density according to sex and age. The purpose of this research was to examine changes in the distribution of bone density in relation to menopause for various future medical purposes and practices related to osteoporosis. DEXA is the most commonly used clinical tool for the diagnosis of osteoporosis. It is considered safe because it has relatively less radiation exposure and a short inspection time. In addition, it can directly measure total bone mass and has a rate of high diagnostic accuracy, sensitivity, and reproducibility. The indicators of bone health are bone mass, BMC, and BMD, while BMD alone is used as a standard for diagnosing osteoporosis [23,24]. In this study, the mean BMD in male and female participants was inversely correlated with age. These findings were similar to the results of [PERSON]'s study [25], which effectively demonstrated that the BMDs of Japanese women in their 20s and 70s were inversely proportional to their age. Moreover, the differences in BMC and BMD between age groups demonstrated the total mineral contents of males aged 20-39 years were the highest when compared to older age groups, and females aged 20-59 years had similar results. In addition, BMC was significantly different between age groups among both male and female participants, with BMC decreasing with age. [PERSON] et al. [26] reported age has the highest inverse correlation with BMD. Other factors associated with BMD included race, family history of osteoporosis, estrogen hormone, calcium intake, weight, and physique. In addition, age was reported as a major predictor of BMD and osteoporosis [27]. In this study, male participants aged 20-39 years had the highest total BMC. Male participants aged 40-59 years also had a relatively high BMC in comparison to male participants aged 60-79 years. Female participants aged 20-39 years and 40-59 years demonstrated a similar pattern of relatively high BMC compared to older female participants (aged 60-73 years). These results are similar to those of previous studies [25,27], which showed a correlation between age and weight as factors that influence bone density. Our results are also consistent with the findings of [PERSON] et al. [25], which showed that Japanese women have low BMDs, and the difference is several times greater for women after menopause. Decreases in BMD and in BMC with increasing age are thought to be due to a decrease in lean mass, and increased bone resorption of osteoclasts caused by the lack of estrogen secretion from the ovaries after menopause. In addition, as noted by [PERSON] and [PERSON] [27], race, family history of osteoporosis, calcium intake, weight, and physique may affect BMD and BMC. Our study was inconsistent with previous studies [28; 29], which demonstrated a slight increase in BMC after the age of 30 years and a rapid decrease after the age of 50 years, both before and after menopause.