What's in a Mean? Comparing Interbeat Interval Averaging Methods Across Variability Levels and Window Lengths

Area of Science:

• Psychophysiology
• Cardiovascular Research

Background:

• Interbeat intervals (IBIs) are crucial for cardiac timing analysis in psychophysiology.
• Current guidelines stress transparent reporting of IBI calculation methods.
• Discrepancies exist between duration-weighted and unweighted IBI averaging methods, with implications for data interpretation.

Purpose of the Study:

• To quantify the consequential differences between duration-weighted and unweighted IBI averaging methods.
• To investigate how within-person variability and window length influence these discrepancies.
• To assess the impact of these methods on cardiac timing metrics.

Main Methods:

• Simulated 5-minute IBI data for 10,000 participants with varying within-person variability (1%–25%).
• Aggregated simulated and real IBI data (N>500 adults) into non-overlapping windows (250–300,000 ms).
• Compared duration-weighted and unweighted mean IBIs across different variability levels and window lengths.

Main Results:

• Increased within-person variability and longer window lengths correlated with larger average discrepancies between methods.
• Real-world data analysis confirmed simulation findings: longer windows increased disagreement.
• Under typical resting conditions (low variability), disagreement was minimal, but could exceed 5% with high variability and long windows.

Conclusions:

• The choice between duration-weighted and unweighted IBI averaging is critical for reducing measurement error.
• Accurate reporting of IBI calculation methods is essential for reliable cardiac timing metric interpretation.
• Methodological choices significantly influence the interpretability of psychophysiological data derived from cardiac timing.