| dc.description.abstract | Background: A dysregulation of the hypothalamic-pituitary-adrenal axis and sympathetic nervous system in patients with Major Depressive Disorder (MDD) has been noted in numerous studies. A recent study has highlighted that the ratio of reactive salivary alpha amylase to salivary cortisol (AOC) may be a better indicator of MDD than either biomarker alone1. Yet no studies thus far have examined whether this ratio can be used with baseline values instead of reactive measurements. This study will investigate the relationship between MDD or depressive symptoms and baseline AOC in patients with symptomatic atherosclerotic disease.
Methods: Data for this study was gathered from the SMART-Medea study, consisting of 614 subjects with symptomatic atherosclerotic disease. Detailed information was gathered on MDD status, through the Patient Health Questionnaire-9 (PHQ-9) and the Composites International Depression Interview. Samples of salivary alpha amylase and salivary cortisol were taken at several time points in a single day2. The SMART-Medea study gathered detailed demographic and lifestyle information allowing for extensive use of demographic, sampling, lifestyle and medication covariate use in this study. This study firstly examined the relationship between PHQ-9 score and AOC through a linear regression analysis. Secondly the difference in AOC values among the three MDD groups (no MDD, subthreshold MDD and MDD) was gathered through an Analysis of Covariance (ANCOVA).
Results: The linear regression with adjustments for age, gender, level of education, smoking, stress, alcohol use, and medication use showed that PHQ-9 score had a significant positive association with AOC at the time points 45 minutes after awakening and 60 minutes after awakening. The other time points do not show a significant association between PHQ-9 score and AOC. Results of the ANCOVA do not show a significant difference in AOC among the no MDD, subthreshold and MDD group for any of the time points or the area under the curve values.
Conclusion: This study is the first to study the effects of MDD and MDD symptoms on the ratio of baseline salivary alpha amylase to salivary cortisol in subjects with symptomatic atherosclerotic disease. Results of this study indicate that AOC is associated with PHQ-9, as a marker for MDD symptom expression, at several time points during the day. An association between MDD group and AOC was not found in this study. | |
