Objective: The present study examines a measure of cardiac autonomic function, the heart rate variability (HRV), in a group of depressed elderly. Cardiac autonomic abnormalities have been implicated as a potential mediator of cardiovascular events and sudden death in depression. Because aging is associated with decreased cardiac vagal activity, it is possible that autonomic abnormalities are even more pronounced in the older depressed patients.
Design: Cross-sectional comparison between those with or without depression. The groups were compared using the Wilcoxon matched-pair sign-rank test.
Setting: Advanced Center for Interventions and Services Research for Late-Life Mood Disorders at University of Pittsburgh Medical Center.
Participants: Fifty-three patients with major depression (mean age: 73.3; SD: 7.4; range: 60-93) and an equal number of age and gender-matched subjects as a comparison group.
Intervention: None.
Measurements: Time domain and frequency domain measures of HRV.
Results: The groups did not differ in any of the time domain or frequency domain measures of HRV. As expected, subjects without depression displayed decreasing cardiac vagal function with aging (Spearman correlation coefficient r(s) = -0.33, p = 0.02). However, there was no significant change in vagal function with age in the depressed (r = 0.12, p= 0.38). Post-hoc analysis using Fisher's z(r) transformation revealed that the relationship between age and cardiac vagal function was significantly different between the groups (z = 2.32, p = 0.02).
Conclusions: Our findings suggest that age has differential influence on vagal function in individuals with and without depression, a difference with implications for cardiovascular disease risk in depression. Prospective studies of cardiac vagal activity in depressed patients with or without preexisting cardiac disease in different age groups are needed to replicate and extend these findings.