Evaluation of ECG Repolarization Parameters in a Worker Cohort Working the Night Shift

Night Shift work is an increasingly common working order that affects human well-being and it is little known about its arrhythmic role in the cardiovascular system. We aimed to investigate the effect of working at night shifts on P-wave dispersion (Pd), QT and QTc dispersions (QTd, QTcd resp) on surface electrocardiography.

We included 286 foundry workers who work at night shift and 100 foundry workers who work on day time only. The night shift workers were divided into three subgroups according to the length of time they worked at night shift. Surface electrocardiography and blood tests were applied for all participants.

Pd, QTd and QTcd values increased in the night shift workers compared to the day time workers (p < 0.05). In subgroup analysis; the night shift workers for more than 15 years had a significantly higher Pd, QTd and QTcd compared to others (p < 0.001). Correlation analysis revealed significant positive correlations with working duration and Pd (r = 0.578, p < 0.001) and QTcd (r = 0.417, p < 0.001). In the linear regression analysis, working duration at night shift was significantly associated with Pd and QTcd values, independent from other associated clinical risk parameters.

This study makes one of the first attempts to assess changes in ECG parameters reflecting tendency to rhythm disturbances, in night shift workers. Our results further underline the importance of covering a comprehensive evaluation of ECG in periodical health check-ups in night shift workers to evaluate the risk of both atrial and ventricular arrhythmias.