The Frequency and Related Factors of Masked Hypertension among Volunteers

Background: 'Masked Hypertension' is a phenomenon of blood pressure that is normotensive by clinic measurement but proves to be hypertensive by 24 hour-AMBP and is associated with many cardiovascular complications and its clinical importance has become the center of public interest. However, in Korea no study concerning masked hypertension has ever been published so far. We investigated the frequency and the related factors of masked hypertension among Koreans. Methods: Overall, 53 volunteers from Incheon and Seoul, Korea, who were 40 years old and abov were enrolled from August 2003 to August 2004. We checked their blood pressure and pulse rate every hour using an ambulatory blood pressure monitoring device [SpaceLabs 90207] for 24 hours. Masked hypertension was defined as office mean BP less than 140/90 mmHg and daytime mean BP over 135/85 mmHg. Results: Among the total, 15 subjects met the criteria of masked hypertension (28.3%) Current smoking (P=0.021), higher clinic mean SBP (P=0.011) and DBP (P=0.027), and prehypertension (P=0.04) were identified as related factors. And when adjusted for sex by logistic regression, only current smoking was statistically significant (P=0.039) and prehypertension showed borderline significance (P=0.092) (CI=95%). Additionally, mean pulse pressures and mean standard deviation of individual mean SBP were higher in the masked hypertension group. Conclusion: The frequency of masked hypertension was 28.3% the and related factors were current smoking and higher office BP, especially prehypertension that was introduced in JNC-7. The fact that the pulse pressure and the variability of individual SBP were higher in the masked hypertension group remains thought-provoking.