Differential Heart Rate Variability Profiles During Sleep in Older Adults with Remitted Early‐onset versus Late‐onset Depression

Background Sleep is a physiological state involving a dynamic autonomic profile that is ideal for detecting subtle changes in autonomic nervous system functioning. The current study sought to determine if heart rate variability (HRV) during different periods of sleep is impaired in older adults with early‐onset (EOD), late‐onset (LOD), and no history of lifetime depression (NOD). Method A total of 188 older adults aged 50‐90 years were recruited from the Healthy Brain Ageing clinic at the Brain and Mind Centre, University of Sydney. This samples comprised 49 participants with EOD, 37 with LOD, and 102 with NOD. Each participant underwent medical, psychiatric and neuropsychological assessments, as well as overnight polysomnography. Result Findings show that for HRV during wake‐after‐sleep‐onset (WASO), only older adults with remitted EOD have significantly lower SDNN and Shannon Entropy, two HRV indices of interest, in comparison to the NOD group, suggesting that those with EOD have diminished overall autonomic function and cardiac complexity respectively. By contrast, older adults with remitted LOD have significantly lower parasympathetic activities during deeper sleep stages (i.e. N2 and N3), as evidenced by a reduction in high‐frequency HRV relative to the EOD group. Overall, our findings suggest that the EOD and LOD phenotypes have differential heart rate profiles during sleep. Conclusion A history of depression, in particular whether this history is early‐ or late‐ onset, is associated with the integrity of autonomic functioning during both wakefulness and sleep in older adults. HRV may have potential as a biomarker of depression and could complement other biomarkers to enhance diagnostic accuracy and prognostic monitoring. As older adults with early‐life depression seem to experience more pronounced autonomic dysfunction, this further emphasizes the need for early and effective interventions, as well as proactive preventative strategies for those with remitted major depressive disorder.