Background
Changes in parasympathetic activity have been associated with depression; however, it is not well understood whether these changes are a result of depression, or represent a compensatory mechanism protecting against it. We examined the association of autonomic nervous system activity with the risk of depression in euthymic individuals and those with subsyndromal depression using heart rate variability (HRV) analysis.
Methods
From a community-based longitudinal cohort, 464 subjects from the baseline assessment and 253 who completed the 5-year follow-up visit were included in the cross-sectional and prospective analyses, respectively. Linear regression analysis was used to investigate the association of HRV measures with the current and future GDS scores. Logistic regression analysis examined the effect of HRV on future risk of SSD.
Results
Low-frequency power (LFN), high-frequency power (HFN), and the LFN/HFN ratio at the baseline assessment were associated with the GDS score at the 5-year follow-up assessment; however, they were not associated with the GDS score at the baseline assessment. High HFN indicated an increased risk of depression at the 5-year follow-up assessment in euthymic subjects (OR = 3.025, 95% CI = 1.184 – 7.726, p = 0.021).
Limitations
HRV was not measured at the follow-up assessment and the interval between the assessments was comparatively long. Five-minute ECG recordings were used, and all participants were 65 years old or older.
Conclusions
Parasympathetic predominance may precede the onset of depression in older adults.
Faculty 
