Assessment of Heart Rate Variability Among Plant Nursery Workers

Objectives: Work-related stress has become prevalent among workers in various occupational sectors, including agriculture. This study assessed stress among seasonal migrant workers at a plant nursery throughout their full work shift. Methods: The study included nine participants who performed a variety of tasks during the measurement day. Their beat-to-beat heart intervals were continuously collected using a heart rate monitor and mobile application. Their stress at work was then characterized in terms of heart rate variability (HRV) parameters (Mean RR, SDNN [Standard Deviation of NN], RMSSD [Root Mean Square of Successive Differences], VLF [Very Low Frequency] Power, LF [Low Frequency] Power, HF [High Frequency] Power, Total Power, VLF%, LF%, HF%, LF n.u. HF n.u. and LF:HF Ratio) using the Kubios HRV software. Generalized linear mixed-effects models were used to determine the effect of time of day since work began (partitioned into 15-min windows) and the assigned job tasks. Results: Time of day was found to reduce Mean RR, SDNN, RMSSD, LF, HF, and Total Power, while increasing the LF:HF ratio, indicating stress increased as the workday progressed. Some job tasks had a significant impact on workers’ stress levels. The task of field maintenance, including trimming bushes and sweeping cut branches, resulted in an increase in workers’ stress. Conversely, weeding appeared to decrease SDNN, RMSSD, and VLF Power, suggesting this activity reduced stress. Conclusion: This study demonstrated the feasibility of assessing heart rate variability in the field, providing objective data to decision-makers. To the authors’ knowledge, this study is among the first to evaluate agricultural workers’ stress using direct physiological measures such as heart rate variability.