medwireNews: Long-term variability in blood pressure (BP), measured in the clinic, is associated with an increased risk of cardiovascular disease (CVD) events and mortality, regardless of mean blood pressure, results of a systematic review and meta-analysis show.
Mid-term (home monitoring) and short-term (ambulatory monitoring) variability showed similar associations, but the researchers note that the data were limited for these outcomes.
These findings could be “particularly important for patients with a highly variable but comparatively low mean blood pressure or for whom traditional cardiovascular risk estimates lie close to treatment thresholds”, say Richard Stevens (University of Oxford, UK) and colleagues.
The research team identified 41 papers, comprising 46 separate analyses in observational and clinical trial cohorts, that assessed the impact of BP variations on CVD events and mortality. The studies included between 457 and 122,636 participants who were followed up for between 2514 and 490,544 person–years.
Of these, 23 analyses were excluded because they did not correctly adjust for mean BP, did not account for major drug changes during the measurement period or did not separate the measurement and follow-up periods, all of which could introduce confounding.
Studies with sufficiently low risk of bias to assess the impact of long-term BP variability showed that an increase in each unit of standardised BP variability (BP variability divided by its sample standard deviation) was associated with an 18% increased risk of both CVD mortality and events, a 15% increased risk of both stroke and all cause mortality and a 10% increased risk of coronary heart disease, independent of mean BP.
And the researchers point out that these associations “are similar in magnitude to those of cholesterol measures with cardiovascular disease.”
Each unit increase in standardised mid-term daytime systolic BP variability was associated with a 15% increased risk of all cause mortality, but a lack of data from distinct studies meant Stevens and team could not assess the other outcomes.
Short-term variability in daytime systolic BP was also associated with an increased all cause mortality risk, at 10%, as well as a 12% increased CVD mortality risk and an 11% increase in the risk of stroke.
“By limiting our main analysis to studies that avoid potential sources of confounding, this review confirms that the apparent prognostic value of blood pressure variability is a true prospective association and can be demonstrated even in studies with low risk of bias”, Stevens and co-authors write in The BMJ.
They conclude: “Future work should focus on the clinical implications of assessment of variability in blood pressure and avoid the common confounding pitfalls observed to date.”
By Laura Cowen
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