Medical Chronobiology Program, Division of Sleep Medicine, Brigham and Women's Hospital, Boston, Massachusetts, USA.
Am J Hypertens. 2013 Jun;26(6):822-8. doi: 10.1093/ajh/hpt026. Epub 2013 Mar 27.
Blood pressure (BP) is highest during the day and lowest at night. Absence of this rhythm is a predictor of cardiovascular morbidity and mortality. Contributions of changes in posture and physical activity to the 24-hour day/night rhythm in BP are not well understood. We hypothesized that postural changes and physical activity contribute substantially to the day/night rhythm in BP.
Fourteen healthy, sedentary, nonobese, normotensive men (aged 19-50 years) each completed an ambulatory and a bed rest condition during which BP was measured every 30-60 minutes for 24 hours. When ambulatory, subjects followed their usual routines without restrictions to capture the "normal" condition. During bed rest, subjects were constantly confined to bed in a 6-degree head-down position; therefore posture was constant, and physical activity was minimized. Two subjects were excluded from analysis because of irregular sleep timing.
The systolic and diastolic BP reduction during the sleep period was similar in ambulatory (-11±2mmHg/-8±1mmHg) and bed rest conditions (-8±3mmHg/-4±2mmHg; P = 0.38/P = 0.12). The morning surge in diastolic BP was attenuated during bed rest (P = 0.001), and there was a statistical trend for the same effect in systolic BP (P = 0.06).
A substantial proportion of the 24-hour BP rhythm remained during bed rest, indicating that typical daily changes in posture and/or physical activity do not entirely explain 24-hour BP variation under normal ambulatory conditions. However, the morning BP increase was attenuated during bed rest, suggesting that the adoption of an upright posture and/or physical activity in the morning contributes to the morning BP surge.
血压（BP）在白天最高，夜间最低。这种节律的缺失是心血管发病率和死亡率的预测因素。体位变化和体力活动对 24 小时昼夜血压节律的影响尚不清楚。我们假设体位变化和体力活动对 BP 的昼夜节律有很大的影响。
14 名健康、久坐、非肥胖、血压正常的男性（年龄 19-50 岁）每人分别完成了一项动态和卧床休息条件下的测量，在 24 小时内每 30-60 分钟测量一次血压。在动态条件下，受测者遵循他们通常的日常生活习惯，不受限制，以捕捉“正常”状态。在卧床休息期间，受测者被持续限制在 6 度头低位的床上；因此，体位保持不变，体力活动最小化。由于睡眠时间不规律，有 2 名受测者被排除在分析之外。
在动态和卧床休息条件下，睡眠期间的收缩压和舒张压下降相似（分别为-11±2mmHg/-8±1mmHg 和-8±3mmHg/-4±2mmHg；P=0.38/P=0.12）。在卧床休息期间，舒张压的早晨高峰减弱（P=0.001），收缩压也有类似的趋势（P=0.06）。
在卧床休息期间，大部分 24 小时 BP 节律仍然存在，这表明在正常日常活动条件下，典型的日常体位变化和/或体力活动并不能完全解释 24 小时 BP 变化。然而，在卧床休息期间，早晨血压升高减弱，这表明在早晨采取直立姿势和/或体力活动有助于早晨血压高峰的形成。
