Short-term HRV dynamics track suicide risk changes in depressive inpatients: A retrospective one-week longitudinal study.
BACKGROUND Heart rate variability (HRV) is a non-invasive marker of autonomic regulation that may be related to suicide risk, but longitudinal evidence in inpatients is limited. This study examined one-week HRV dynamics and suicide-risk reduction in depressive inpatients. METHODS This retrospective one-week longitudinal study included 177 inpatients with major depressive disorder (MDD) or bipolar disorder (BD) during a depressive episode. Suicide risk was assessed using the Mini-International Neuropsychiatric Interview (MINI), and HRV was measured at admission and after one week. Patients were classified as low suicide risk (LSR, n = 96) or moderate-to-high suicide risk (MHSR, n = 81). Linear mixed-effects models and multivariable regression were used. RESULTS The MHSR group was younger (FDR-P = 0.003) and had higher Hamilton Depression Rating Scale scores (FDR-P = 0.005). At admission, the MHSR group showed higher average heart rate (AHR) and low-frequency/high-frequency ratio (LF/HF), and lower standard deviation of normal-to-normal intervals (SDNN), root mean square of successive RR interval differences (RMSSD), and high-frequency power (HF) (all FDR-P ≤ 0.05); these differences were no longer significant at week 1. RMSSD showed a significant time × group interaction (FDR-P = 0.026). Greater suicide-risk reduction was associated with decreased AHR (FDR-P = 0.041) and increased SDNN, RMSSD, total power (TP), low-frequency power (LF), and HF (all FDR-P < 0.001). CONCLUSIONS Higher suicide risk was associated with altered autonomic regulation at admission. HRV changes over one week were associated with suicide-risk reduction, suggesting that HRV may provide dynamic physiological information for longitudinal inpatient suicide-risk monitoring.