Effect of shift work on blood pressure in middle aged workers

我们在24小时内对正常血压和高血压轮班工人每15分钟监测一次血压(BP)和心率(HR)，其中白班和夜班各一次。血压和心率的昼夜变化几乎完全逆转，血压正常的工人从白班转换到夜班。然而，在高血压工人中，昼夜节律模式并未完全逆转，即上夜班时血压和心率降至一天中0000至0400之间的最低水平。因此，我们发现正常血压和高血压工人在倒班工作和一天中的不同时间对血压和心率的影响存在差异。在实验室条件下，我们比较了三种应激负荷试验(心算、冷脸试验和直立倾斜)对血压的反应性，这三种负荷试验每天分别在0900、2100和0300测量三次。高血压受试者在0300度直立倾斜时血压显著下降，而他们的心输出量在测试过程中没有变化。我们推测，午夜时分高血压患者的外周血管阻力增加等机制可能受损，这也与高血压轮班工人血压水平在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.