By Afsaneh Gray, medwireNews Reporter
A systematic review and meta-analysis of studies investigating the link between visit-to-visit variability (VVV) of blood pressure (BP) and cardiovascular disease (CVD) or all-cause mortality has revealed a modest, but significant, association.
However, the authors caution that: “Additional studies using standardized approaches for estimating VVV of BP are needed to clarify its prognostic value.”
Thirty-seven studies comprising 41 separate patient cohorts were selected for analysis. Studies had to meet certain criteria, such as the inclusion of only adult participants, the measurement of blood pressure on at least three visits on separate days, and follow-up for outcomes of CVD, coronary heart disease (CHD), stroke or mortality. The majority of papers selected were published between 2010 and June 2014, the cut-off point.
Cohorts varied greatly, ranging from 144 to 58,228 participants. Some were general population/community-based samples, but others were of elderly populations, individuals with hypertension, a history of stroke, on haemodialysis, those with chronic kidney disease but not on haemodialysis, individuals with Type 2 diabetes and postmenopausal women.
The researchers also found that the number of visits used to derive VVV ranged from three to 156 visits, with the time interval between visits varying from 2 days to 3–4 years. Studies considered different measures of VVV, with the most common being standard deviation (SD) and coefficient of variation (CV), and looked at different measures of blood pressure (systolic, diastolic, pulse pressure and mean arterial pressure).
Despite this variability of methodology, across all studies the VVV of systolic and diastolic blood pressure showed significant associations with outcomes in 58% of 312 and 32% of 188 analyses, respectively.
Unfortunately, few studies provided sufficient data to pool risk estimates but where this was possible, analyses showed an association between VVV and risk estimates. The pooled hazard ratio for stroke across seven cohorts was 1.17 for each 5 mmHg increase in SD of systolic blood pressure, for CHD across four cohorts it was 1.27, for CVD across five cohorts it was 1.12, for CVD mortality across five cohorts it was 1.22 and for all-cause mortality across four cohorts it was 1.20.
Increased VVV of diastolic BP was associated with an increased risk of CHD and CVD mortality.
Nonetheless, lead author Keith Diaz (Columbia University, New York, USA) and colleagues point out that “[i]n many cases, the positive findings within a cohort were accompanied by additional analyses wherein no association was observed.”
Writing in the journal Hypertension, they conclude: “Future studies using rigorous methodology should be conducted to provide a better assessment of the VVV of BP–outcome association and determine the clinical usefulness of measuring VVV of BP.”
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