The morning surge in blood pressure and heart rate is dependent on levels of physical activity after waking.
Level 4 - case-series / case-control
Cross-sectional observational study analyzing simultaneous 24-hour ambulatory blood pressure monitoring and actigraphy
PubMed 12011646 · doi:10.1097/00004872-200205000-00020
What was done
Simultaneous 24-hour ambulatory blood pressure monitoring and actigraphy were performed in 420 patients. The morning surge was defined as the difference between mean blood pressure and heart rate in the 4-hour periods before and after waking, and trough-to-peak surge was also calculated. Surges were regressed against the difference in log-transformed mean physical activity between these periods, adjusted for age, sex, clinic blood pressure, and antihypertensive medication use using multiple linear regression.
What was found
Mean morning surges were 23/15 (± 13/10) mmHg for blood pressure and 17 (± 10) beats/min for heart rate, while the geometric mean increase in physical activity after waking was 33 (± 1.5) units. Magnitudes of systolic blood pressure, diastolic blood pressure, and heart rate surges all positively and significantly correlated with the increase in physical activity from before to after waking (P < 0.005). Greater clinic blood pressure was also significantly associated with a greater activity-related morning blood pressure surge (P < 0.0005).
Why it matters
The post-waking rise in blood pressure and heart rate is substantially driven by physical activity upon rising. Physical activity must be accounted for when interpreting ambulatory blood pressure monitoring records.
Limits
As an observational cross-sectional study, it cannot establish whether controlling activity-induced surges alters cardiovascular outcomes. The abstract does not describe the specific patient population, clinical indications for monitoring, types of antihypertensive medications, or sleep quality.
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