Cardiovascular Risk of White-Coat Hypertension
What is the role of white-coat hypertension (WCH) and the white-coat-effect (WCE) in the development of cardiovascular disease (CVD)?
The authors used the 11-cohort IDACO (International Database on Ambulatory Blood Pressure Monitoring in Relation to Cardiovascular Outcomes) to compare daytime ambulatory blood pressure monitoring (APBM) with conventional BP measurements in 653 untreated patients with WCH and 653 normotensive controls. European Society Hypertension guidelines were used to calculate a 5-point risk score (exclusive of hypertension): low risk = 0 to 2 risk factors versus high risk = ≥3 to 5 risk factors, diabetes, and/or history of prior CVD events. Age- (within 5 years) and cohort-matching was done between the two groups for fatal and nonfatal outcomes. WCE was calculated as the systolic or diastolic conventional BP minus the daytime ABPM.
Overall WCH was present in 11.3% of normotensives based on ABPM (cohort ranged from 3.6% to 35%). In a stepwise linear regression model, systolic WCE increased by 3.8 mm Hg (95% confidence interval [CI], 3.1-4.6 mm Hg) per 10-year increase in age, and was similar in low- and high-risk patients with or without prior CVD events. Over a median 10.6-year follow-up, incidence of new CVD events was higher in 159 high-risk patients with WCH compared with 159 cohort- and age-matched high-risk normotensive patients (adjusted hazard ratio [HR], 2.06; 95% CI, 1.10-3.84; p = 0.023). The HR was not significant for 494 participants with low-risk WCH and age-matched low-risk normotensive patients. Subgroup analysis by age showed that an association between WCH and incident CVD events is limited to older (≥60 years) high-risk WCH patients; the adjusted HR was 2.19 (95% CI, 1.09-4.37; p = 0.027) in the older high-risk group and 0.88 (95% CI, 0.51-1.53; p = 0.66) in the older low-risk group (p for interaction = 0.044). The increment in incident CVD occurred in 3.4% of the 653-person WCH group.
White-coat BP effect size is related to aging, not to CVD risk. CVD risk in most persons with WCH is comparable to age- and risk-adjusted normotensive controls.
WCE is thought to be related to the alerting reaction via the sympathetic nervous system. It was a surprise to me that this study found the degree was independent of CVD risk. Clinicians should consider ABPM in patients suspected of WCH, particularly isolated systolic hypertension in the elderly not excluded by home BP.
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