The importance of using 24-hour and nighttime blood pressure for the identification of white coat hypertension: Data from the Jackson Heart Study

We calculated the prevalence of white coat hypertension (WCH) using out-of-clinic blood pressure (BP) in the daytime period; daytime and 24-hour periods; and daytime, 24-hour, and nighttime periods among 199 African Americans with clinic-measured systolic/diastolic BP 140/90mmHg in the Jackson Heart Study. Left ventricular mass index (LVMI) was measured among participants with WCH and 374 participants with sustained normotension (ie, non-hypertensive clinic, daytime, 24-hour, and nighttime BP). The prevalence of WCH was 29.6%, 21.1%, and 10.6% using daytime BP; daytime and 24-hour BP; and daytime, 24-hour, and nighttime BP, respectively. Compared with sustained normotension, LVMI was higher when WCH was defined using daytime BP (adjusted mean difference [95% CI] 5.0 [-0.2, 10.1] g/m(2)), but not when defined using daytime and 24-hour BP or daytime, 24-hour, and nighttime BP (adjusted mean difference [95% CI] 3.9 [-1.9, 9.7] and 0.4 [-7.3,8.2] g/m(2), respectively). Using only daytime BP overestimates the prevalence of WCH among African Americans.