Although cortisol is believed to increase the osteoclast activity and accentuate bone resorption, few studies are available on cortisol and bone density. This study uses salivary cortisol to investigate the relationship thereof with bone density. Furthermore, we investigated whether the salivary Ca concentration could be an effective biomarker in bone evaluations using salivary cortisol. This study targeted 188 healthy female college students (18 - 25 years old). Calcaneus bone density (Speed of Sound: SOS) was measured using an ultrasonic bone density measurement device. Food intake was calculated via a food intake frequency survey. The saliva of subjects was collected in order to measure the cortisol concentration using an enzyme immunoassay, while the salivary Ca concentration was measured using an atomic absorption spectrophotometer. The relationship between salivary cortisol and SOS was not significant, with a correlation coefficient of -0.13, indicating a negative correlation and leading to the observation that those with lower salivary cortisol levels tended to have higher SOS. The relationship between salivary cortisol and salivary Ca concentration was not significant, with a correlation coefficient of +0.15, indicating a positive correlation and leading to the observation that those with higher salivary cortisol concentrations tended to have higher salivary Ca concentrations. No significant correlation was observed in the relationship between salivary Ca concentration and SOS. Because the cortisol in saliva responds more sensitively to acute stress than to chronic stress, this may not have had obvious significance. Furthermore, the salivary Ca concentration indicated large fluctuations, depending on the daily external conditions, particularly in terms of food; therefore, it is believed that the presence or absence of dietary intake before the survey affected the results. The above results suggest that bone density may decrease, while salivary Ca concentration may increase when salivary cortisol concentration increases due to stress.
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