Background and Purposes: Excessive morning blood pressure surge (MBPS) has been demonstrated to be a predictor of cerebrovascular events and cardiovascular target organ damage. To date, the question on whether the MBPS correlates with blood pressure (BP) reactivity to mental stress remains to be determined. Moreover, the reproducibility of the MBPS as a predictor remains uninvestigated. This study examined the stability of the MBPS and its relation to BP reactivity in untreated hypertensives.

Method: Thirty-six community-dwelling hypertensive individuals, aged 20 to 55, participated in this study. Participants were all newly diagnosed with hypertension and had never been treated with anti-hypertensive medications. All participants were tested at baseline for anthropometric measurements, BP, and heart rate (HR). They were also subject to a laboratory-induced stress protocol. Ambulatory BP monitoring was carried out three times on a weekday (weeks 1, 5, and 12).

Results: The correlation coefficients of the MBPS measurements between weeks 1 and 5, weeks 5 and 12, and weeks 1 and 12 were 0.41, 0.38, 0.57, respectively (all p<0.05). The difference in MBPS between weeks assessed by the paired t-test was not statistically significant. However, the within-subject coefficient of variation was large (18.3% - 32.8%). The agreement between measurements taken on different weeks assessed by the Bland-Altman analysis demonstrated that the limits of agreement between any one pair of measurements (i.e., week 1 versus 5, week 5 versus 12, and week 1 versus 12) were large and not clinically acceptable. The MBPS correlated with nighttime BP (p = 0.001), but not morning BP or BP reactivity. Dippers had greater MBPS than nondippers did (p < 0.05).

Conclusions: The MBPS is not a stable measure over time. An exaggerated pattern of stress reactivity can not explain the link between cardiovascular events and MBPS in the middle-aged mild hypertensives without organ damage.