The relationships among endogenous cortisol, subjective stress, and bone mineral density in non-elderly women
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The study was conducted to determine the relationships among endogenous cortisol (determined by salivary cortisol), subjective (perceived) stress and BMD in non-elderly women. A sample of 38 women between the ages of 30 and 65 years, without a previous diagnosis of osteoporosis, and who were not taking glucocorticoids was obtained to examine the relationships among endogenous cortisol, subjective stress and bone mineral density (BMD). This study also sought to determine whether salivary cortisol or subjective stress were predictive of bone mineral density in this population. These determinations were based on Pearson product moment correlation coefficients. Step-wise multiple correlation analysis was used to determine the variables that are significant predictors of BMD. Independent variables considered in the equation were age, race, family history of osteoporosis, body mass index, alcohol use, cigarette smoking, caffeine intake, dietary calcium intake, calcium supplementation, use of hormone replacement therapy, and weight bearing physical activity. Endogenous cortisol was found to positively correlate with BMD; however, the association was modest. The relationship between subjective stress and BMD was not statistically significant. After controlling for selected extraneous variables, the relationship between cortisol and BMD remained statistically significant. Regression analysis indicated that 20% of the variance of BMD can be attributed to the combined effects of caffeine and alcohol intake; however, caffeine had a greater association. Cortisol levels were not associated with scores on the Index of Clinical Stress, a measure of subjective stress. Additional findings included a modest but statistically significant inverse relationship between caffeine intake and BMD, and a weak but statistically significant positive relationship between alcohol consumption and BMD. A final finding, though not pertaining to BMD, was a statistically significant inverse association between calcium intake and blood pressure.