Associations of Age and Work Type with PPG-Based Heart Rate Variability in Police Officers : A Short-Term Recording Analysis

Background: Police fficers may experience sustained physiological stress due to high-risk duties and irregular shift work. Research using objective physiological indicators is therefore needed. Purpose: This study examined the effects of work type and age on autonomic nervous system-related variability indices among police officers and considered the need for preventive health management. Methods: Of 187 initial records(99 day-shift and 88 rotating-shift records), cases with missing values in seven key variables were excluded using listwise deletion. For duplicate measurements from the same participant, only one record was retained based on signal reception quality and the most recent measurement date. The final complete-case sample consisted of 125 police officers(60 day-shift and 65 rotating-shift officers). Although PPG-based variability is strictly defined as pulse rate variability(PRV), the term HRV was used throughout the manuscript for comparison with previous studies and was conservatively interpreted as a proxy for ECG-based HRV. Welch’s t-test, Pearson’s correlation analysis, and moderated regression analysis were performed. Results: None of the mean differences in variability indices between work-type groups were statistically significant. Age was significantly and negatively correlated with several indices, including SDNN, RMSSD, LF(ln), and HF(ln), and its main effect remained significant in the moderated regression analyses. However, the interaction between work type and age was not significant in any model. Conclusion: The findings did not support the hypothesis that shift work additionally intensifies age-related reductions in variability indices. PPG-based variability indices were more closely associated with chronological age than with work type. Preventive health management based on individual baselines and repeated measurements should be considered.