Effect of shift work on cardio-vascular function -A comparison between normotensive and hypertensive subjects-

本研究的目的是调查轮班工作对血压和心血管功能的影响，并确定是否有正常血压和高血压受试者之间的这种影响的差异。本研究的受试者为10名血压正常的男性，9名未服药的高血压男性和9名服用抗高血压药物的男性。采用日本Koden无创血压监测仪记录白班和夜班24 h动态血压（ABP）。结果：（1）血压在白天和夜间均随活动量的增加而变化，夜间血压随活动量的增加而变化，夜间血压随活动量的增加而变化。(2)血压正常者基础血压（睡眠时最低血压）值夜班高于白班，差异有统计学意义。(3)血压正常者和高血压者的工作时间平均血压在白班和夜班之间无差异。(4)服用降压药的受试者中，夜间工作后即刻的血压高于白天工作后。(5)在高血压患者中，夜班工作时间血压标准差大于白班。(6)加速度计测量的血压、心率与活动量之间存在线性正相关。夜班时心率较白班时减慢，提示夜班对正常血压者和高血压者心血管功能均有影响。在高血压受试者中，外部刺激的影响似乎是更大的夜班比白班。此外，在血压正常的受试者中，我们发现夜间轮班睡眠期间的血压水平高于白天轮班。

Aims of this study are to investigate effects of shift work on blood pressure and cardio-vascular function, and to identify whether there are differences in such effects between normotensive and hypertensive subjects. The subjects of this study were 10 normotensive men, 9 hypertensive men without medication, and 9 men under anti-hypertensive medication. Ambulatory blood pressure (ABP) during 24 hours in daytime shift and in nighttime shift was recorded by the non-invasive devise (Nihon-Koden). Also physical activities, heart rates and postures were measured by lightweight portable monitor (GMS, Activetracer AC301).Results; (1) Blood pressures were changed according to activity level in both daytime and nighttime. (2) Among normotensive subjects, the basal blood pressures (the lowest blood pressure during sleeping) were higher in nighttime shift than in daytime shift with statistical significance. (3) The mean blood pressures during work-time weren't different between daytime shift and nighttime shift for normotensive subjects arid hypertensive subjects. (4) Among subjects under anti-hyoertensive medication, the blood pressures immediately after nighttime work were higher than that after daytime work. (5) Among the subjects with hypertension, the standard deviations of blood pressure during working time were larger in nighttime shift than in daytime shift. (6) There are positive linear regression between blood pressure, heart rate and activities measured by accelometer. The heart rates during night shift decreased compared with those during daytime shift.These results suggested that nighttime shift had effects on cardio-vascular function to both normotensive and hypertensiove subjects. Among hypertensive subjects, the effects of extrinsic stimulation seemed to be larger during nighttime shift than daytime shift. Also among normotensive subjects, we found higher blood pressure level during sleep between nighttime shifts than daytime shift.