Background: Differences in blood pressure (BP) recorded by either doctors or nurses (white coat effect) may be an important factor in the association between BP variability and clinical outcomes. Visit-to-visit Systolic BP (SBP) variability has been shown to be a strong predictor of cardiovascular events. The aim of the current analysis is to determine whether the association between visit-to-visit SBP variability and cardiovascular events is similar for BP measured by doctors in comparison to nurse measurements.
Methods: Data from 49844 visits of 5953 patients aged >65 years from ANBP2 were used. Visit-to-visit SBP variability was defined as within-individual standard deviations in SBP across visits and categorized into higher (top quartile) and lower (lower three quartiles) variability. Cox-proportional hazard models were used to explore the relationship between cardiovascular events and SBP variability.
Results: Visit-to-visit SBP variability was a strong predictor for cardiovascular events. The hazard ratio (95% confidence interval) for any first cardiovascular event with SBP variability was 1.64 (1.39 - 1.92), for stroke 2.21 (1.60-3.06), for myocardial infarction 1.85 (1.24-2.75) and for heart failure 2.36 (1.65-3.38) after adjusting for sex, age, treatment allocation and SBP at randomization. The association remained comparable when BP was measured either by doctors or clinic nurses.
Conclusions: There is no evidence of a white coat effect for SBP variability assessment which remains a strong predictor of cardiovascular outcomes in elderly treated hypertensives. Reducing visit-to-visit SBP variability might be an additional target for cardiovascular risk reduction in elderly patients additional to management of elevated absolute BP levels.
(C) 2012 Lippincott Williams & Wilkins, Inc.