Although depression and anxiety predict risk of cardiac mortality, the contributions of depression and anxiety to vagal cardiac control have not been systematically evaluated. The goal of this study was to examine the relationship between state anxiety and vagal control of heart rate in older adults with major depressive disorder (MDD). Older adults (50-70 years old) were selected for this study because of the greater cardiac risk associated with low vagal cardiac control across this age range.
Fifty-six men and women with MDD were evaluated. MDD was diagnosed using the Diagnostic Interview Schedule, and severity of depression was measured using the Beck Depression Inventory and the Hamilton Rating Scale for depression. State anxiety was measured using the Spielberger State Anxiety Inventory. Power spectral analysis was used to measure two indices of vagal control: baroreflex control of heart rate (BRCSPEC) and respiratory sinus arrhythmia (RSA).
State anxiety was negatively correlated with levels of BRCSPEC (r = -0.32, p < .05), whereas depression severity was not related to either RSA or BRCSPEC. Furthermore, BRCSPEC was reduced by approximately 33% in MDD patients with state anxiety scores (ST-ANX) in the highest quartile (ST-ANX > 41, N = 13), compared with patients with ST-ANX scores in the lowest quartile (ST-ANX < 25, N = 14; p < .05).
Anxiety, but not depression severity, is associated with reduced BRCSPEC in older men and women. Future studies are needed to determine whether comorbid anxiety contributes to the increased cardiovascular risk associated with MDD.