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Night-time Systolic Blood Pressure Linked to Cardiovascular Events


Presented by George C. Roush, USA

Night-time systolic blood pressure (SBP), but not daytime or clinic SBP, can predict future cardiovascular events (CVEs), despite adjusting for multiple variables and type of SBP measurement. George C. Roush, MD, St. Vincent’s Medical Center, Bridgeport, Connecticut, USA, presented data from a meta-analysis of the prognostic effect of clinic, daytime, and night-time SBP from 9 international cohorts.

Current data are unclear as to which type of SBP – daytime, night-time, or clinic – is the most predictive of CVEs. Potential limitations of current data include inadequate sample sizes, imprecise classification of daytime versus night-time SBP, and no adjustment for all 3 types of SBP. The purpose of this study was to correct for some of these limitations to determine which type of SBP is most predictive of CVEs.

In this meta-analysis, a systematic review included 9 studies with a combined sample size of 13844 patients reported through PubMed and OVID that studied hypertension with ≥1 years of follow-up and with CVE as the outcome. A post-hoc analysis was performed that was adjusted for sex, age, smoking status, diabetes mellitus, and baseline BP treatment. The cohort-level analyses included dispersion and coefficient of variation with standard deviation from the mean times 100%.

Greater dispersion in night-time SBP was observed in all 9 cohorts compared with daytime SBP (p=0.004). In addition, night-time SBP (HR, 1.27; 95% CI, 1.20 to 1.34) was associated with a greater risk of CVEs, whereas daytime (HR, 1.01; 95% CI, 0.91 to 1.11) or clinic SBP (HR, 1.00; 95% CI, 0.97 to 1.04) were not, even with simultaneous adjustment for the 3 types of SBP of the 6 highest quality cohorts (Table 1). In addition, night-time SBP was associated with a greater risk of coronary artery disease (CAD; HR, 1.22) and stroke (HR, 1.26). Daytime SBP was not associated with CAD or stroke.

The cohort-level of analysis is a limitation of this study, but the strengths of this study include a large sample size, ability to evaluation relationships in different populations, inclusion of high quality cohorts, and patient-specific night-day classification of SBP.

Night-time SBP elevation is important because even modest variations within the normal BP range of <140/90 mmHg result in an increased risk of CVEs [Vasan RS et al. N Engl J Med 2001]. Dr. Roush suggested that night-time SBP may be critical for several reasons, including increased vulnerability of target organs to increases in artery pressure due to decreased arteriolar tone at night.

Dr. Roush concluded the data from this meta-analysis suggest that night-time SBP has greater dispersion than other types of SBP measurements, and that night-time SBP predicts risk for CVEs.



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