Reduced heart rate variability during mania in a repeated naturalistic observational study

Area of Science:

• Neuroscience
• Psychiatry
• Cardiology

Background:

• Bipolar disorder (BD) is a chronic mood disorder linked to autonomic nervous system (ANS) dysfunction, measured by heart rate variability (HRV).
• Longitudinal studies on HRV changes between mood states in BD are limited.
• This study investigates within-individual HRV differences between manic and euthymic states.

Purpose of the Study:

• To longitudinally compare heart rate variability (HRV) in individuals with bipolar disorder during manic and euthymic states.
• To identify specific HRV metrics associated with mood state changes in bipolar disorder.
• To explore the relationship between ANS function and mood fluctuations in bipolar disorder.

Main Methods:

• A longitudinal observational study involving 15 bipolar disorder patients.
• Overnight heart rate data collected using photoplethysmography (PPG) wristbands in both manic and euthymic states.
• Analysis of HRV metrics including RMSSD, HF, LF, VLF, Total Power, and Sample Entropy, compared using paired t-tests and regression.

Main Results:

• All measured HRV metrics were significantly lower in the manic state compared to the euthymic state (p ≤ 0.02).
• Effect sizes for HRV changes ranged from medium to large (g = 0.65–1.24).
• Age and sex did not significantly influence HRV changes between mood states.

Conclusions:

• Lower HRV in manic states compared to euthymia indicates significant autonomic nervous system dysregulation in bipolar disorder.
• Findings support the association between ANS dysfunction and mood state changes in bipolar disorder.
• Further longitudinal research with larger sample sizes is recommended to clarify these associations.