THE LONG-TERM REPRODUCIBILITY OF THE WHITE-COAT EFFECT ON BLOOD PRESSURE AS A CONTINUOUS VARIABLE: THE OHASAMA STUDY

Abstract

Objective: White coat hypertension is defined as a condition in which office blood pressure (BP), but not out-of-office BP, is elevated. However, the hypertension phenotype categorized by a determined threshold is generally fluctuant in individuals with BP readings close to the hypertension threshold. Furthermore, there is little information about the reproducibility of the white coat effect, which was a continuous variable, over more than a 1-year interval. The present study investigated the long-term interval reproducibility of the white coat effect. Design and method: We used the repeatedly measured white coat effect (office BP and home BP) at a 4-year interval in 153 participants not undergoing antihypertensive treatment (men, 22.9%; mean age, 64.4 years) from the general population of Ohasama, Japan. The reproducibility of the white coat effect as a continuous variable was assessed by testing the Bland–Altman plot and intraclass correlation coefficient (two-way random effect model single measures). Results: At baseline, the mean values were 127.5±15.8 mmHg for office systolic BP, 120.3±11.3 mmHg for home systolic BP, and 7.2±12.8 mmHg for the white coat effect based on systolic BP. The white coat effect for systolic BP decreased by 0.17±14.53 mmHg at the 4-year visit. The Bland–Altman plots showed no significant systemic error for the white coat effect (P > = 0.24) (Figure). The intraclass correlation coefficient (95% confidence interval) of the white coat effect for systolic BP, office systolic BP, and home systolic BP were 0.41 (0.27–0.53), 0.64 (0.52–0.74), and 0.74 (0.47–0.86), respectively. The difference in office systolic BP strongly contributed to the large change in the white coat effect. The agreements between hypertension phenotypes at baseline and the 4-year visit were minimal (kappa = 0.36; 95% confidence interval, 0.25–0.48). Conclusions: Long-term reproducibility of the white coat effect is limited in the general population not undergoing antihypertensive treatment. The change in the white coat effect is mainly caused by office BP variation.