Abstract:

Objective · To analyze the association of morning hypertension with heart rate and heart rate variability and explore the association between sympathetic activity and morning hypertension. Methods · We recruited outpatients who visited the Department of Hypertension from Nov. 2010 to Jun. 2015 and were suspected of hypertension with no anti-hypertensive treatment. The 24 h ambulatory blood pressure was monitored and time domain and frequency domain indexes of heart rate variability were measured. The morning hypertension was defined as a mean systolic blood pressure of at least 135 mmHg or a mean diastolic blood pressure of at least 85 mmHg within 2 hours after getting up in the morning. Results · Of 596 subjects, 354 (59.4%) had morning hypertension. The Logistic regression analysis showed that the risk of morning hypertension increased with heart rates in sitting and supine positions, increased heart rate within 24 h and low frequency (LF) heart rate variability in supine position (P<0.01). After adjustments for sex, age, body mass index, cigarette smoking, alcohol consumption, fasting blood glucose, and serum total cholesterol, the associations of morning hypertension with 24 h heart rates and LF heart rate variability were still statistically significant (P<0.05). Conclusion · Morning hypertension is associated with increased heart rate and LF heart rate variability, indicating the association between morning hypertension and activated sympathetic system.

Key words: morning hypertension, ambulatory blood pressure monitoring, heart rate, heart rate variability