Cardiovascular dysfunction due to shift work

Electrocardiographic, biochemical, and physical data obtained from 237 shift and 115 day workers without any obvious disorders were assessed to clarify the impact of shift work on cardiovascular functions. The heart-rate corrected QT interval (QTc) was significantly longer in the shift workers than in the day workers. However, blood pressure, working duration, and biochemical and other data were comparable between the two work groups. When multiple regression analysis was used, shift/day work was significantly related to the QTc in all of the workers. The adjusted odds ratio of shift work to the prolonged QTc (> or = 440 ms1/2) was 8.15. The prolonged QTc has been thought to contribute to an increased risk of cardiac death. These findings, therefore, suggest that the increased risk for cardiovascular mortality in shift workers may be attributable to prolongation of the QTc.