Effect of shift work on blood pressure in middle aged workers

在24小时内，我们采用无创门诊方法每15分钟监测一次血压（BP）和心率（HR），一次在白班，一次在夜班。在正常血压的工人中，从白班到夜班的转换几乎完全逆转了血压和心率的昼夜变化。然而，在高血压工人中，昼夜节律模式并没有完全逆转，即夜班时的血压和HR在0000至0400之间降至一天中的最低水平。因此，我们发现在轮班工作和工作时间对血压和心率的影响上，正常血压和高血压患者存在差异。在实验室条件下，我们比较了血压对三种压力负荷测试（心算、冷脸测试和抬头倾斜）的反应性，这些测试每天在0900、2100和0300测量三次。高血压受试者在0300仰卧时血压明显下降，而心输出量在试验期间无变化。我们推测高血压患者的外周血管阻力增加等机制可能在午夜时分受损，这也与高血压轮班工人的血压水平在0000 - 0400之间下降有关。

We monitored blood pressure (BP) and heart rate (HR) every 15 minutes over 24 hours by a noninvasive ambulatory method in normotensive and hypertensive shift workers, once while on the day shift and once while on the night shift. The circadian variations in BP and HR were almost completely reversed with the switch from the day shift to the night shift in normotensive workers. In hypertensive workers, however, the circadian pattern was not completely reversed, i.e. BP and HR while on the night shift dropped to the lowest level of the day between 0000 and 0400. Thus, we found differences between normotensive and hypertensive workers in the effects of shift work and time of day on BP and HR.In a laboratory condition, we compared reactivity of blood pressure to three stress loading tests (mental arithmetic, cold face test, and head-up tilt) which were measured three times a day at 0900, 2100 and 0300. Blood pressure significantly declined during head-up tilt at 0300 in the hypertensive subjects, while their cardiac output showed no change during the test. We speculated that some mechanisms such as increasing the peripheral vascular resistance might be impaired in the hypertensive subjects during midnight, which is also related to the drop of blood pressure level between 0000 and 0400 in the hypertensive shift workers.