Objective: The purpose of this study is to analyze heart rate variability on the light therapy for shift worker in electronics industry.
Background: Although the shift work system could be improved productivity, it has been reported that the inconsistency of the circadian rhythm negatively affects worker's health such as physical, psychological and psychosocial activities.
Method: This study participated in eighteen female workers in their 20s and 30s. They have been working in shift for more than six months in the electronics manufacturing process. For the heart rate signal measured during work, heart rate signals were sampled in a continuous 60-minute interval within 120 minutes after the starting (early) and before ending (last) of the working period. This study evaluated the time domain heart rate variability (HRV) of Mean NN, SDNN, SDANN, SDNN index, RMSSD and pNN50. For the Wilcoxon signed-rank test, this study analyzed the significant difference between the HRV in the early and last of working period according to the light therapy.
Results: For the non-light therapy group, there were significant difference of HRV of Mean NN, RMSSD and pNN50 between early and late of working period. These HRV were analyzed to be significantly increased in the late of working period than in the early work period. In non-light therapy group, most of HRV showed high variability.
This reason is that worker's psychological tension was alleviated in relation to the finish time at the late of working period. For the light therapy group, there were no significant difference of all HRV between early and late of working period. It showed that the light therapy group should keep maintained stability of autonomic nervous system compared to the non-light therapy group.
Conclusion: This study suggested a method that the light therapy could be reduce variability in heart rated and improve stability for shift worker. And RMSSD and pNN50 of HRV could effectively evaluate the activation of the autonomic nervous system among HRV in the time domain.
Application: Based on the result of this study, non-invasive light therapy could contribute to the prevention of occupational diseases and improving work quality in the shift work system.